Bi 1:
Frame relayFrame relay vn l cng ngh WAN c trin khai nhiu nht c dng router. c mt s chuyn i dn dn t FR sang cc cng ngh nh VPN da trn nn IP v MPLS-VPN. Tuy nhin Frame relay s vn ng mt vai tr ln trong cc mng doanh nghip trong mt tng lai trc mt. Chun FR c pht trin bi nhiu nhm nghin cu. Ban u, Cisco v cc cng ty khc (cn c gi l gang of four) pht trin mt chun gip cho tnh tng thch ca FR v pht trin sn phm. Sau mt din n v Frame relay Framerelay Forum c thnh lp nhm pht trin FR. IETF hin nh ngha vi RFC lin quan n vic dng FR nh l giao thc lp 2 trong mng IP. Ti liu Cisco IOS thng m t cc chun ca FR thng qua cc tho hip hin thc FRF, v d FRF.12 lin quan n c t cho tin trnh phn mnh. Cui cng, ANSI v ITU xy dng trn cc chun ny chun ha FR theo chun quc gia ca M v quc t. Cc mch o ca Frame Relay: Cng ngh Frame Relay thng chuyn cc frame t ngun n ch trn nhng ng dn kt ni o. Cc ng i o ny c th l cc mch o thng trc (permanent virtual circuits - PVCs) hoc cc mch o chuyn mch (switched virtual circuits - SVCs). Mt PVC thng c thit lp bi cc nh cung cp dch v khi h lp trnh cc tng i Frame Relay Switch. Ty thuc vo tho thun vi nh cung cp, mt khch hng hoc mt PVC ca ngi dng c th c cu hnh mang lu lng n mt tc no c gi l tc thng tin cam kt (committed information rate - CIR). CIR l tc truyn m mng Frame Relay hoc nh cung cp ng truyn trong tnh trng bnh thng, y cng l tc trung bnh trong mt khong thi gian no . n v ca CIR l bits trn giy. Mi kt ni PVC cui mi thit b u cui c xc nh bng mt a ch c chiu di 10 bit trong phn header u ca frame, cn c gi l DLCI. DLCI thng c dng nh x n a ch lp mng ca ch n, tc a ch ca router u xa ca mch PVC. Sau d liu cn c truyn trn h tng Frame relay s c ng gi trong cc header ny. Mi header trong Frame Relay c chn vo gi tr DLCI tng ng n a ch lp mng ca ch n. Cc frame sau s c gi n tng i vi gi tr DLCI ban u. Cc frame ny tip tc c trung chuyn v pha mng ch
thng qua cc tng i ca cc nh cung cp dch v FR. Cc tng i FR c th thay i gi tr DLCI sang cc PVC khc trn ng i v ch. Kt qu l, gi tr DLCI ca mt frame khng nht thit phi l ging nh gi tr ban u khi frame i vo mng Frame Relay. V vy, gi tr DLCI ch c ngha cc b. Ngoi ra, c hai u ca PVC c th dng cng gi tr DLCI, v d DLCI 200. Tuy nhin, cui mt kt ni, mt DLCI khng th tng trng cho nhiu hn mt PVC. Thng s nhn dng kt ni lp datalink DLCI : kt ni hai thu bao Frame Relay DTE, nh cung cp dch v FR s dng mt mch o gia hai router u cui. Mt router c th gi ra mt frame Frame Relay, trong c mt trng c chiu di 10-bit nhn dng tng VC, gi l Data Link Connection Identifier (DLCI). Cc tng i trung gian FR chuyn cc frame da trn thng tin trn gi tr DLCI ca frame, cho n khi frame thc s thot ra khi tng i n router trn u kia ca kt ni. Cc gi tr FR DLCI ch c ngha cc b, ngha l mt gi tr DLCI no ch c ngha trn mt kt ni n. Kt qu l gi tr DLCI ca mt frame c th thay i khi frame i qua mt mng. Nm bc di y hin th cc gi tr DLCI cc b cho mt mch o trong hnh v.
Router A gi ra mt frame vi gi tr DLCI 41. Tng i FR xc nh frame l mt phn ca mch VC kt ni router A n routerB. Tng i FR thay th trng DLCI ca frame bng gi tr 40. Trong thc t, mt vi nh cung cp dch v dng a ch DLCI ton cc. Qui c DLCI truyn thng cho php ta suy ngh router c mt a ch n duy nht, cng tng t nh vai tr ca a ch MAC. Tuy nhin cc a ch vn l cc b v mt gi tr DLCI ca mt mch o VC vn c th b thay i gi tr khi n i qua mt h thng mng. V d, cho cng mt VC t routerA n RouterB, ch ra routerA c DLCI l 40 v routerB c DLCI l 41. tng ca a ch ton cc th cng ging nh trong LAN. V d, khi router A gi mt frame n Router B, router A s gi frame n a ch ton cc ca router B (41). Tng t, routerB s gi mt frame n a ch ton cc ca router A (40). Cc thng ip qun l trng thi cng ni b (Local Management Interface LMI) Cc thng ip LMI trong FrameRelay gip ta qun l trng thi ng truyn gia router thu bao v tng i FR. Mt router thu bao dch v FR c th gi cc thng ip truy vn v trng thi n tng i v tng i s tr li bng thng ip trng thi LMI Status thng bo cho router v gi tr DLCI ca mch o VC cng nh l trng thi ca tng mch VC ny. ch mc nh, thng ip LMI c gi mi 10 giy. C mi thng ip th su s mang y thng tin v trng thi, trong bao gm thng tin y hn v tng VC. Cc thng ip truy vn LMI Status enquiry (t router) v Status (t tng i) cng hot ng nh c ch keepalive. Mt router s xem cc cng ca n l b hng nu router khng th nhn thng ip t tng i trong ba chu k (mi chu k l 10 giy). Kt qu l, c ch LMI trong Frame Relay thc s c cho php hoc khng c cho php bng cch dng lnh keepalive/no keepalive trn cng Frame Relay ca router. Ni cch khc, lnh no keepalive s tt cc thng ip LMI. C ba loi thng ip LMI tn ti, ch yu l do c nhiu nh cung cp thit b v cc chun khc nhau pht trin FR. Kiu c nh ngha sm nht, c gi l Cisco LMI th hi khc vi cc kiu ANSI v ITU c nh ngha sau . S khc nhau im: Cisco LMI cho dng cc gi tr DLCI c php, tc dy s DLCI cho php. Cc gi tr DLCI c dng gi thng ip LMI.
Ni mt cch thc t, cc vn ny t quan trng. Mc nh router s t ng d tm loi LMI. Nu cn thit, lnh frame-relay lmi-type c th c dng ch ra kiu LMI c dng trn ng truyn Frame Relay. Bng di y lit k ba kiu LMI, t kha type cng vi vi im so snh lin quan n LMI v cc gi tr DLCI cho php. V d kiu LMI ca Cisco cho php dng cc gi tr DLCI t 16 cho n 1007. Kiu LMI ca ANSI cho php dng DLCI t 16 n 991. Gi tr DLCI c dng bi chnh LMI truyn v nhn cc thng ip cng khc nhau. Cisco LMI dng DLCI 1023, cn ANSI LMI dng DLCI 0.
Frame Relay Headers v qu trnh ng gi FR Router to ra cc frame bng cch dng cc header lin tip khc nhau. Header u tin l ITU Link Access Procedure for Frame-Mode Bearer Services (LAPF). Header LAPF bao gm tt c cc trng c dng bi tng i FR phn phi cc frame trn m my FR, cc trng ny bao gm DLCI, DE, BECN v FECN. Cc trng theo sau phn LAPF s cha cc thng tin quan trng cho cc router thu bao trn u cui ca VC. i vi on header ng gi, c hai ty chn tn ti: Cc loi header do Cisco nh ngha ban u. Header c nh ngha bi IETF trong RFC 2427 (trc y l RFC 1490). Nu ta dng Cisco router cui mi VC, tu chn cisco l ph hp v lm vic tt. Trong khi, ty chn ietf l cn thit trong trng hp dng nhiu sn phm ca cc hng khc nhau. C hai header u c mt trng c tn l protocol h tr nhiu giao thc lp 3 trn mt VC. Trng c dng nhiu nht l trng xc nh giao thc lp mng Network Layer Protocol ID, c m t trong RFC2427. Hnh di y m t cu trc ca header v trailer.
Mi VC mc nh u dng header ca Cisco tr phi c cu hnh dng header kiu IETF. C ba phng thc c dng cu hnh mt VC dng kiu header IETF: Dng lnh encapsulation frame-relay ietf. Lnh ny s thay i trng thi mc nh ca cng sang IETF thay v dng cisco. Dng lnh frame-relay interface-dlci number ietf, b qua trng thi mc nh cho VC ny. Dng lnh frame-relay map dlci.ietf. Lnh ny cng s thay i trng thi mc nh ca VC. V d, trn mt cng c 10 VC, trong c by VC cn phi dng kiu ng gi IETF, cng c th chuyn sang IETF bng lnh encapsulation frame-relay ietf. Sau , lnh frame-relay interface-dlci number cisco c th c dng cho ba VC cn chy theo kiu ng gi Cisco. Cc tn hiu bo nghn DE, BECN v FECN trong Frame Relay Mng FR, cng ging nh cc mng a truy cp khc, c th to ra nghn do vn tc khng ng b. V d mt mng Frame Relay c 20 thu bao vi cc ng 256 kbps v mt vn phng chnh c bng thng mc T1. Nu c 20 site gi cc frame lin tc v vn phng chnh cng mt thi im, ta s c khong 5Mbps d liu cn i ra khi ng T1 1.5Mbps, lm cho hng i ca tng i FRSwitch tng nhanh. Tng t, khi vn phng chnh cn gi d liu n bt k chi nhnh no, router s gi tc T1. iu ny l nguyn nhn tim tng gy nghn u ra, cc hng i cng c th tng nhanh chng bn trong mng FrameRelay. Do , FR cung cp hai phng thc phn ng vi vn nghn. Adaptive Shaping, FECN v BECN chng 16, shaping v policing m t khi nim nh hnh lu lng
theo ch thch ng, trong router s thay i tc nh hnh ty thuc vo mng c nghn hay khng. phn ng vi nghn xy ra trong mng FR, router phi nhn c vi dng thng bo t tng i FRSwitch rng nghn xy ra. V vy phn header ca FR s bao gm cc bit Forward Explicit Congestion Notification (FECN) v bit Backward Explicit Congestion Notification (BECN) bits bo hiu nghn xy ra trn mt VC no . thc hin vic ny, khi mt tng i FRSwitch nhn thy c nghn gy ra bi mt VC, tng i s gn bit FECN trong mt frame ca VC . Tng i cng theo di cc VC ang b nghn sao cho n c th tm ra frame k tip ang c gi trn VC nhng i theo chiu i din nh trong bc 4 ca hnh. Tng i sau s nh du bit BECN trong frame ang truyn theo chiu ngc li ny. Router nhn c frame c bit BECN bit rng mt frame do router gi ra chu tnh trng nghn, v vy router c th gim tc gi d liu ca n xung. Hnh di y m t mt v d ca tin trnh.
Bit FECN c th c gn bi tng i FR nhng khng th c gn bi bt k router no bi v router khng cn truyn tn hiu nghn. V d, nu R1 ngh rng nghn xy ra t tri sang phi, R1 c th ch cn gim tc truyn xung. u kia ca kt ni, R2 l ch n ca frame, v vy n s khng bao gi lu v nghn xy ra cho nhng frame i t tri sang phi. V vy, ch c tng i cn phi thit lp gi tr bit FECN. BECN th c th c gn bi tng i v bi router. Hnh trn m t mt tng i gn gi tr BECN trn frame k tip ca ngi dng. N cng c th gi cc frame kim tra Q.922. ng thi ny gip loi b s cn thit phi ch cho c lu lng ca ngi dng gi trn VC v gn gi tr BECN trn frame . Cui cng, cc router c th c cu hnh xem xt cc frame c bit FECN, phn ng li bng cch gi ra cc frame kim tra Q.922 trn VC vi bit BECN c thit lp. c tnh ny, thnh thong cn c gi l phn hi FECN. Tnh nng ny c cu hnh bng lnh shape fecn-adapt (CB Shaping) hoc lnh traffic-shape fecn-adapt (FRTS).
Bit ch ra kh nng loi b frame DE Khi c nghn xy ra, cc hng i trong tng i FRSwitch bt u lp y. Trong vi trng hp, frame c th b loi b ra khi hng i. Tng i c th (nhng khng yu cu) phi kim tra bit ch ra kh nng loi b ca frame Discard Eligibility (DE) khi frame cn phi b loi b. Tng i FR s ch ng loi b cc frame c bit DE thay v loi b cc frame khng c bit DE. C router v tng i FR c th gn bit DE. Thng thng, mt router s ra quyt nh v vic gn bit DE trong vi frame no , bi v ngi qun tr c kh nng bit cc lu lng no l quan trng hn lu lng no, thng l chiu inbound. nh du cc bit DE c th c thc hin thng qua c ch CB Marking, dng lnh set fr-de ca MQC. Mc d router thng thc hin vic nh du bit DE, cc tng i FR cng c th nh du bit DE. i vi tng i, ng tc nh du thng c thc hin khi tng i khng ch lu lng, nhng thay v loi b cc lu lng vt qu gii hn, tng i s nh du bit DE. Bng cch ny, cc tng i bn di s c kh nng loi b cc frame nh du v gy ra nghn. Bng di y tm tt cc im mu cht v FECN, BECN v bit DE
Cu hnh Frame Relay Phn ny m t cc cu hnh c bn v cc lnh hot ng, cng vi cc c ch nn ti trn FR v c ch chn LFI trong FR. Cu hnh Frame Relay c bn Hai chi tit quan trng nht lin quan n cu hnh Frame Relay l vic kt hp cc gi tr DLCI vi cc cng hoc subinterface v vic nh x a ch lp 3 n cc gi tr ny. Mt iu th v l c hai c im ny c th c cu hnh vi cng hai lnh: frame-relay map v lnh frame-relay interface-dlci.
Mc d mt router c th hc cc gi tr DLCI trn ng truyn FR thng qua cc thng ip LMI, cc thng ip ny khng c chc nng ngm nh rng DLCI s dng cho cng no. cu hnh FR dng cc subinterface, cc thng s DLCI phi c kt hp vi cc subinterface. Bt k DLCI no c hc vi LMI m khng kt hp vi mt cng subinterface th s c gi s l dng cho cng vt l. Mt phng thc ph bin hn thc hin vic kt hp ny l dng lnh frame-relay interface-dlci trong du nhc lnh sub interface. Trn cc subinterface dng im-ni-im point-to-point, ch c mt lnh frame-relay interface dlci l c php dng, trong khi nu cng l dng a im multipoint, c th nhiu lnh c dng. Mt phng thc thay th l dng lnh frame-relay map. Lnh ny vn nh x a ch lp 3 sang gi tr DLCI nhng cng ngm nh ch ra rng DLCI thuc v cng m lnh ny c cu hnh. Trn cc cng subinterface dng a im, nhiu lnh c th c cho php i vi tng giao thc lp 3. V d di y m t cc ty chn cu hnh ca FR, dng lnh frame-relay interface-dlci v cc lnh show lin quan. V d ny hin thc cc yu cu sau y: R1 dng nhiu cng dng multipoint subinterface kt ni R2 v R3. R1 dng cc cng subinterface dng im-im kt ni n R4. Mch o VC gia R1 v R4 dng kiu ng gi IETF.
Bt u bng cu hnh ca R1. Cng subinterface s0/0.14 hin th ty chn IETF c dng trn lnh frame-relay interface-dlci. Cng subinterface s0/0.123 c hai DLCI thuc v n, l VC kt ni n R2 v R3. Code: interface Serial0/0/0 encapsulation frame-relay ! interface Serial0/0.14 point-to-point ip address 10.1.14.1 255.255.255.0 frame-rely interface-dlci 104 IETF ! interface Serial0/0/0.123 multipoint ip address 101.123.1 255.255.255.0 frame-relay interface-dlci 102 frame-relay interface-dlci 103 Tip theo l cu hnh R2. R2 gn gi tr DLCI cho VC t R1 v R3 n cng subinterface .123. Ch rng s ca subinterface ca router khng cn phi ng bng gi tr DLCI. Code: interface Serial0/0/0 encapsulation frame-relay ! interfacce Serial0/0/0.123 multipoint ip address 101.123.2 255.255.255.0 frame-relay interface-dlci 101 frame-relay interface-dlci 103 Tip theo l cu hnh R4, trong ng gi bng lnh frame-relay ietf. Lnh ny s thit lp kiu ng gi cho tt c cc VC trn cng S0/0/0. Cng lu rng tn sut gi cc thng ip thay i t gi tr mc nh (10) thnh 8 thng qua lnh keepalive 8. Code: interface Serial0/0/0 encapsulation frame-relay IETF keepalive 8 ! interface Serial0/0/0.1 point-to-point ip address 10.1.14.4 25.255.255.0 frame-relay interface-dlci 101
Lnh show frame-relay pvc hin th cc thng tin thng k v trng thi ca tng VC. Lnh k tip trn R1 b qua mt s on, ch li nhng dng c trng thi PVC. Code: R1# show frame-relay pvc| incl PVC STATUS DLCI = 100, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0/0 DLCI = 102, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0.123 DLCI = 103, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0.123 DLCI = 104, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0.14 DLCI = 105, DLCI USAGE = UNUSED, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0 DLCI = 106, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0/0 DLCI = 107, DLCI USAGE = UNUSED, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0 DLCI = 108, DLCI USAGE = UNUSED, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0 DLCI = 109, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0/0 Code: R1# show frame-relay pvc 102 PVC Statistics for interface Serial0/0/0 (Frame Relay DTE) DLCI = 102, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0.123 input pkts 41 output pkts 54 in bytes 4615 out bytes 5491 dropped pkts 0 in pkts dropped 0 out pkts dropped 0 out bytes dropped 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 27 out bcast bytes 1587 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec pvc create time 00:29:37, last time pvc status changed 00:13:47 Kt qu lnh di y xc nhn rng ng truyn ca R1 ang dng Cisco LMI. Cc thng ip trng thi LMI s xut hin mi pht trong thng ip Full Status message c lit k sau cng. Ch rng router gi cc thng ip truy vn trng thi n tng i. Khi tng i gi cc thng ip trng thi, cc b m ny s cng tng. Code:
R1# show frame-relay lmi LMI Statistics for interface Serial0/0/0 (Frame Relay DTE) LMI TYPE = CISCO Invalid Unnumbered info 0 Invalid Prot Disc 0 Invalid dummy Call Ref 0 Invalid Msg Type 0 Invalid Status Message 0 Invalid Lock Shift 0 Invalid Information ID 0 Invalid Report IE Len 0 Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 183 Num Status msgs Rcvd 183 Num Update Status Rcvd 0 Num Status Timeouts 0 Last Full Status Req 00:00:35 Last Full Status Rcvd 00:00:35 Lnh show interface lit k vi chi tit, bao gm cc khong thi gian gi cc thng ip LMI, LMI stats, LMI DLCI v cc trng thi trong hng i FR. Hng i broadcast gi cc broadcast FR m nhng broadcast ny s c nhn bn v gi trn VC. V d nh cc OSPF LSAs. Code: R1# show int s 0/0/0 Serial0/0/0 is up, line protocol is up ! lines omitted for brevity Encapsulation FRAME-RELAY, loopback not set Keepalive set (10 sec) LMI enq sent 185, LMI stat recvd 185, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 1023 LMI type is CISCO frame relay DTE FR SVC disabled, LAPF state down Broadcast queue 0/64, broadcasts sent/dropped 274/0, interface broadcasts 228 ! Lines omitted for brevity Code: R3# sh frame lmi |include LMITYPE LMI Statistics for interface Serial0/0/0 (Frame Relay DTE) LMI TYPE = ANSI R3# sh int s 0/0/0 | include LMI DLCI LMI DLCI 0 LMI type is ANSI Annex D frame relay DTE Ch l R3 ang dng kiu ANSI LMI. R3 c th cu hnh LMI tnh bng cu lnh frame-relay lmi-type {ansi | cisco | q933a} trong cng vt l. Tuy nhin R3 b qua lnh ny, lm cho R3 c hnh ng mc nh l t ng tm ra loi LMI.
Frame Relay Inverse ARP: IP ARP c bit n nh mt giao thc ph thng v tng i n gin. i vi k thi CCIE cng vy. a s cc cu hi trong phn IP ARP l nhng cu hi n gin. Do , nhng cu hi kh v ch xy dng CEF adjacency table s tp trung vo Frame Relay Inverse ARP, cng chnh v vy m phng thc Frame Relay Inverse ARP s c trnh by c th v chi tit hn. Tng t nh IP ARP, nhim v ca InARP l phn gii gia a ch L3 v a ch L2. a ch L3 chnh l a ch IP, cn a ch L2 y chnh l s DLCI (tng t nh a ch MAC trong IP ARP). Tuy nhin, trong phng thc InARP, router bit c a ch L2 (DLCI), v cn phn gii ra a ch L3 (IP) tng ng. Hnh sau l mt v d v chc nng ca InARP.
Trong mi trng LAN, i hi phi c mt gi tin (ARP request) n host v kch hot giao thc IP ARP trn host (tr v ARP reply). Tuy nhin , trong mi trng WAN, khng cn mt gi tin no n router kch hot InARP trn router ny, thay vo l mt thng ip v tnh trng LMI (Local Management Interface) s c dng. Sau khi nhn c thng ip trng thi LMI l LMI PVC Up, router s loan bo a ch IP ca n ra mch lin kt o (VC - Virtual Circuit) tng ng thng qua thng ip InARP (nh ngha trong RFC1293). Nh vy, mt khi LMI khng c thc thi th InARP cng khng hot ng bi v khng c thng ip no ni cho router bit gi thng ip InARP.
Trong mng Frame Relay, nhng cu hnh chi tit c chon la vi mc ch trnh mt s tnh trng khng mong mun, nhng tnh trng ny s c m t chi tit trong nhng trang k tip ca chng ny. V d khi s dng point-topoint subinterface, vi mi VC thuc mt subnet ring, tt c nhng vn gp phi trong cu hnh ny s c m t r rng c th phng trnh. Bn thn giao thc InARP tng i n gin. Tuy nhin, khi trin khai InARP trn nhng m hnh mng khc nhau, da trn nhng kiu cng khc nhau (cng vt l, cng point-to-point subinterface v multipoint subinterface) th cch thc hot ng ca InARP s tr nn phc tp hn rt nhiu. Sau y l mt v d v h thng mng Frame Relay c thit k theo m hnh mng li khng y (partial mesh) trn cng mt subnet trong khi mi router s dng mt kiu cng khc nhau.
S mng trn ch mang tnh cht l mt v d, n ch s dng trong mi trng hc tp hiu chi tit hn v cch thc hot ng ca InARP. S ny khng nn c p dng trong mi trng mng thc t bi thit k yu km vi nhiu hn ch khi trin khai giao thc nh tuyn bn trn. Thng tin ca mt s lnh show v debug lin quan n Frame Relay InARP v mt trong s nhng iu k quc v InARP lin quan n point-to-point subinterface c m t trong v d 1.1. u tin cu hnh frame relay trn cng multipoint ca R1.
Code: Router1# sh run ! Lines omitted for brevity interface Serial0/0 encapsulation frame-relay interface Serial0/0.11 multipoint ip address 172.31.134.1 255.255.255.0 frame-relay interface-dlci 300 frame-relay interface-dlci 400 ! Lines omitted for brevity K tip, cng serial c tt v bt v cc hng trong InARP trc b xa v vy ta c th quan st tin trnh InARP. Code: Router1# conf t Enter configuration commands, one per line. End with CNTL/Z. Router1(config)# int s 0/0 Router1(config-if)# do clear frame-relay inarp Router1(config-if)# shut Router1(config-if)# no shut Router1(config-if)# ^Z Cc thng ip t lnh debug frame-relay event hin th cc thng ip nhn c InARP trn R1. Ch cc gi tr hex 0xAC1F8603 v 0xAC1F8604, vi cc gi tr thp phn tng ng l 172.31.134.3 and 172.31.134.4 (tng ng vi Router3 v Router4). Code: Router1# debug frame-relay events *Mar 1 00:09:45.334: Serial0/0.11: FR ARP input *Mar 1 00:09:45.334: datagramstart = 0x392BA0E, datagramsize = 34 *Mar 1 00:09:45.334: FR encap = 0x48C10300 *Mar 1 00:09:45.334: 80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00 *Mar 1 00:09:45.334: AC 1F 86 03 48 C1 AC 1F 86 01 01 02 00 00 *Mar 1 00:09:45.334: *Mar 1 00:09:45.334: Serial0/0.11: FR ARP input *Mar 1 00:09:45.334: datagramstart = 0x392B8CE, datagramsize = 34 *Mar 1 00:09:45.338: FR encap = 0x64010300 *Mar 1 00:09:45.338: 80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00 *Mar 1 00:09:45.338: AC 1F 86 04 64 01 AC 1F 86 01 01 02 00 00 K tip, ch lnh show frame-relay map c bao gm t kha dynamic, ngha l cc hng c hc thng qua InARP. Code: Router1# show frame-relay map
Serial0/0.11 (up): ip 172.31.134.3 dlci 300(0x12C,0x48C0), dynamic, broadcast, status defined, active Serial0/0.11 (up): ip 172.31.134.4 dlci 400(0x190,0x6400), dynamic, broadcast, status defined, active Trn R3, lnh show frame-relay map ch lit k mt hng duy nht nhng nh dng th khc. Bi v R3 dng point-to-point subinterface, hng ny khng c hc thng qua InARP v kt qu lnh khng bao gm t kha Dynamic. Cng ch l kt qu khng cho thy a ch Layer 3 no. Code: Router3# show frame-relay map Serial0/0.3333 (up): point-to-point dlci, dlci 100(0x64,0x1840), broadcast status defined, active Ch : Trong v d trn ta thy xut hin lnh do trong ch cu hnh. Lnh do cho php cu hnh trong configuration mode nhng thc hin chc nng exec mode m khng phi thot khi mode configuration. V d lnh do clear frame-relay inarp thc hin configuration mode tng ng vi vic ta thc hin lnh clear frame-relay inarp ch ton cc. Trong v d trn, lnh show cho thy Router R1 nhn v s dng thng tin InARP; tuy nhin Router R3 th khng s dng thng tin InARP nhn vo. H iu hnh Cisco IOS hiu rng ch mt VC c thit lp vi mt subinterface point-to-point; mi mt a ch IP u cui khc trn cng mt subnet ch c th tham chiu n duy nht mt s DLCI. V vy, mi thng tin InARP nhn c lin kt n s DLCI l khng cn thit. Ly v d, khi no Router R3 cn gi mt gi tin n Router R1(172.31.134.1), hay n mi u cui khc trong subnet 172.31.134.0/24. T chnh cu hnh ca mnh, Router R3 bit rng phi gi qua s DLCI trn point-to-point subinterface , ngha l qua DLCI 100. V vy, mc d c ba kiu cng c dng cho cu hnh Frame Relay h tr InARP mt cch mc nh, point-topoint subinterface s b qua thng tin InARP nhn c. Cu hnh nh x a ch tnh trong Frame Relay Trong hnh 1.3, R3 bit cch y gi tin n R4, nhng ngc li R4 cha bit cch y gi tin ngc tr li Router3. Theo nghi logic R3 s hiu nh sau nhng gi tin n c next-hop router trn subnet 172.31.124.0/24, R3 s gi chng ra theo mt s DLCI trn point-to-point subinterface, y chnh l DLCI 100 . Nhng gi tin ny s c chuyn n R1 v nh R1 chuyn n R4. Trong cch thit k yu km trong hnh 1.3, mc d R4 v R3 s dng hai kiu cng khc nhau, R3 s dng point-to-point subinterface trong khi R4 s dng cng vt l. n c R3, R4 cn gi frame qua DLCI 100 n R1 v nh
R1 chuyn tip n R3. Trong trng hp ny InARP s khng gip c g, bi v thng ip InARP ch cho php qua mt VC, m khng cho php chuyn tip; mt ch thch rng khng c VC no tn ti gia R4 v R3. gii quyt vn ny, trong cu hnh ca R4 c thm vo cu lnh frame-relay map. V d 1.2 m t chi tit thng tin trc v sau khi s dng lnh frame-relay map. Router 4 ch lit k mt hng trong lnh show frame-relay map bi v Router4 ch c mt VC duy nht kt ni v Router1. Ch vi mt VC, Router 4 c th hc v mt router khc thng qua InARP. Code: Router4# sh run ! lines omitted for brevity interface Serial0/0 ip address 172.31.134.4 255.255.255.0 encapsulation frame-relay Router4# show frame-relay map Serial0/0 (up): ip 172.31.134.1 dlci 100(0x64,0x1840), dynamic, broadcast,, status defined, active ! Next, proof that Router4 cannot send packets to Router3s Frame Relay IP address. Router4# ping 172.31.134.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.31.134.3, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) K tip, cc thng tin nh x tnh c thm vo trn Router4 dng lnh framerelay map trong sub-interface. Cng ch rng lnh ny dng DLCI 100, v vy bt c gi tin no c gi bi R4 v 172.31.134.3 (Router3) s i qua VC v router 1, sau li cn nh tuyn gi tin ngc v Router3. T kha broadcast bo cho Router4 gi cc bn copy trn VC ny. Code: Router4# conf t Enter configuration commands, one per line. End with CNTL/Z. Router4(config)# int s0/0 Router4(config-if)# frame-relay map ip 172.31.134.3 100 broadcast Router4(config-if)# ^Z Router4# ping 172.31.134.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.31.134.3, timeout is 2 seconds: !!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/20/20 ms V d 1.2 Ch : Router R3 khng cn phi s dng cu lnh frame-relay map, bi v trong cu hnh ca R3 s dng point-to-point subinterface. Phi nh k rng bn ng nn s dng nhiu kiu cng khc nhau nh hnh 1.3, cng khng nn trin khai m hnh dng li khng y (non-full-mesh) vi cng mt subnet, tr khi bn buc phi thc hin trn ng khng gian a ch IP hn ch ca mnh. Trong trng hp khi bn s dng m hnh nh hnh 1.3, bn c th s dng cu hnh trn. Mt s la chon khc l nu nh bn s dng multipoint subinterface trn c R3 v R4, c hai router u phi s dng cu lnh framerelay map, bi v c hai router u khng th nghe c thng ip InARP t router khc. Tuy nhin, nu c hai router R3 v R4 u s dng point-to-point subinterface, khng router no i hi phi c cu lnh frame-relay map, bi v theo ngha logic c hai router u hiu l: dng mt VC ca n n tt c cc a ch trong subnet. Tt InARP Trong hu ht nhng m hnh mng c a ra, vic s dng InARP l hp l. Tuy nhin, ta c th tt InARP trn interface vt l hay multipoint interface i bng cch s dng lnh no frame-relay inverse-arp trn interface subcommand. C th ngng hot ng InARP trn tt c cc VC ca interface/subinterface, tt c cc VC ca interface/subinterface ng vi mt giao thc L3 ring bit, hay n thun l trn mi DLCI c th. Cu lnh no frame-relay inverse-arp khng ch lm cho router ngng vic gi thng ip InARP ra ngoi, m cn lm cho router khng nhn thng ip InARP. Ly v d, cu lnh no frame-relay inverse-arp ip 400 mode subinterface trn Router R1 trong v d 1.2 khng ch ngn R1 ngng gi thng ip InARP ra DLCI400 ti R4 m cn lm cho R1 b i thng ip InARP nhn trn DLCI400.
(*) Interface point-to-point lun lun b qua thng ip InARP, bi v i vi point-to-point interface, ch dng mt s DLCI gi n tt c a ch trong cng mt subnet Bi 3: SPANNING TREE PROTOCOL - STP 1. Tng quan v IEEE 802.1D: Mt mng mnh m c thit k khng ch em li tnh hiu qu cho vic truyn cc gi hoc frame, m cn phi xem xt lm th no khi phc hot ng ca mng mt cch nhanh chng khi mng xy ra li. Trong mi trng lp 3, cc giao thc nh tuyn s dng con ng d phng n mng ch khi con ng chnh b li th s nhanh chng tn dng con ng th 2. nh tuyn lp 3 cho php nhiu con ng n ch gi nguyn tnh trng hot ng ca mng v cng cho php cn bng ti qua nhiu con ng. Trong mi trng lp 2 (switching hoc bridging), khng s dng giao thc nh tuyn v cng khng cho php cc con ng d phng, thay v bridge cung cp vic truyn d liu gia cc mng hoc cc port ca switch. Giao thc Spanning Tree cung cp lin kt d phng mng chuyn mch lp 2 c th khi phc t li m khng cn c s can thip kp thi. STP c nh ngha trong chun IEEE 802.1D.
1.1. Spanning Tree l g v ti sao phi s dng n? Spanning Tree Protocol (STP) l mt giao thc ngn chn s lp vng, cho php cc bridge truyn thng vi nhau pht hin vng lp vt l trong mng. Sau giao thc ny s nh r mt thut ton m bridge c th to ra mt topology lun l cha loop-free. Ni cch khc STP s to mt cu trc cy ca free-loop gm cc l v cc nhnh ni ton b mng lp 2. Vng lp xy ra trong mng vi nhiu nguyn nhn. Hu ht cc nguyn nhn thng thng l kt qu ca vic c gng tnh ton cung cp kh nng d phng, trong trng hp ny, mt link hoc switch b hng, cc link hoc switch khc vn tip tc hot ng, tuy nhin cc vng lp cng c th xy ra do li. Hnh 3.1 biu din mt mng switch in hnh v cc vng lp c c dng cung cp kh nng d phng nh th no.
Hai nguyn nhn chnh gy ra s lp vng tai hi trong mng chuyn mch l do broadcast v s sai lch ca bng bridge. Broadcast Loop Broadcast Loop v vng lp lp 2 l mt s kt hp nguy him. Hnh 3.2 biu din broadcast to ra vng lp phn hi (feedback loop).
Gi s rng, khng c switch no chy STP: Bc 1: host A gi mt frame bng a ch broadcast MAC (FF-FF-FF-FFFF-FF). Bc 2: frame n c hai Cat-1 v Cat-2 qua port 1/1 Bc 3: Cat-1 s a frame qua port 1/2. Bc 4: frame c truyn n tt c cc node trn on mng Ethernet k c port 1/2 ca Cat-2. Bc 5: Cat-2 a frame ny n port 1/1 ca n. Bc 6: mt ln na, frame xut hin port 1/1 ca Cat-1. Bc 7: Cat-1 s gi frame ny n port 1/2 ln hai. Nh vy to thnh mt vng lp y. Ch : frame ny cng trn qua on mng Ethernet v to thnh mt vng lp theo hng ngc li, feedback loop xy ra trong c hai hng. Mt kt lun quan trng na trong hnh 3.2 l bridging loop nguy him hn nhiu so vi routing loop. Hnh 3.3 m t format ca mt DIXv2 Ethernet frame.
DIXv2 Ethernet Frame ch cha 2 a ch MAC, mt trng Type v mt CRC. Trong IP header cha trng time-to-live (TTL) c thit lp ti host gc v n s c gim bt mi khi qua mt router. Gi s b loi b nu TTL = 0, iu ny cho php cc router ngn chn cc datagram b run-away. Khng ging nh IP, Ethernet khng c trng TTL, v vy sau khi mt frame bt u
b loop trong mng th n vn tip tc cho n khi ai ngt mt trong cc bridge hoc ngt mt kin kt. Trong mt mng phc tp hn mng c m t trong hnh 3.1, 3.2 th c th gy ra feedback loop rt nhanh theo t l s m. V c mi frame trn qua nhiu port ca switch, th tng s frame tng nhanh rt nhiu. Ngoi ra cn phi ch n broadcast storm trn cc user ca host A v B trong hnh 3.2. Broadcast c x l bi CPU trong tt c cc thit b trn mng. Trong trng hp ny, cc PC u c x l broadcast storm. Nu ta ngt kt ni mt trong s cc host t LAN, th n hot ng tr li bnh thng. Tuy nhin, ngay khi ta kt ni n tr li LAN th broadcast s s dng 100% CPU. Nu ta khng x l iu ny m vn tip tc s dng mng, th s to ra vng lp vt l trong VLAN. Vic sai lch bng bridge: Nhiu nh qun tr switch/bridge nhn thc vn c bn ca broadcast storm, tuy nhin ta phi bit rng thm ch cc unicast frame cng c th truyn mi trong mng m cha vng lp. Hnh 3.4 m t iu ny. Bc 1: host A mun gi gi unicast n host B, tuy nhin host B ri khi mng, v ng vi bng bridge ca switch khng c a ch ca host B. Bc 2: gi s rng c hai switch u khng chy STP, th frame n port 1/1 trn c hai switch. Bc 3: v host B b down, nn Cat-1 khng c a ch MAC BB-BB-BBBB-BB-BB trong bng bridge, v n trn frame qua cc port. Bc 4: Cat-2 nhn c frame trn port 1/2 . C 2 vn xy ra. o Bc 5: Cat-2 trn frame v n khng hc a ch MAC BB-BB-BB-BB-BBBB, iu ny to ra feedback loop v lm down mng. o Cat-2 ch rng, n ch nhn mt frame trn port 1/2 vi a ch MAC l AA-AA-AA-AA-AA-AA. N thay i a ch MAC ca host A trong bng bridge dn n sai port.
V frame b lp theo hng ngc li, nn ta thy a ch MAC ca host A b ln gia port 1/1 v 1/2. iu ny khng ch lm mng b trn vi cc gi unicast m cn sa sai bng bridge. Nh vy khng ch c broadcast mi lm h hi mng. --------------------------Bi 4:
Spanning Tree.Mt h thng mng hin thc STP km c th dn n rt nhiu cng vic cu hnh, khi phc li trn mng campus. Bi vit ny gii thch c ch hot ng ca spanning-tree, chc nng ngn nga loop trong mng switch. STP l mt trong nhng ch m tnh k thut trong cng ngh LAN switching. hiu v STP th cng kh khn nh l hiu v cc c ch hot ng bn di ca OSPF hay EIGRP (timers, kiu gi tin, cc gii thut). STP ng vai tr nn tng trong hot ng ca mi h thng mng campus. N ng vai tr then cht trong thit k v trin khai mng campus. Spanning-tree l mt giao thc lp 2 s dng mt gii thut c bit tm ra cc vng lp trong mng v tc ng ca mt mng khng b loop. STP s to ra mt cu trc cy bao gm cc l v cc nhnh tri rng trn ton b mng L2. Trong phn ny, thut ng switch v bridge c dng thay th ln nhau. Ngoi ra, nu khng cp n, kt nI gia cc switch s c gi s l kt ni trunk. Cc vng lp loop c th din ra trong mt h thng mng v nhiu l do. Thng thng, loop l kt qu ca nhng c gng xy dng cc kt nI d phng. Tuy nhin, loop cng c th dn n t nhng li do cu hnh.
Cc kt ni vt l theo kiu vng lp m khng dng STP c th gy nhiu vn . C hai vn c th dn n l broadcast loop v hng bng mac-address. Mt frame Ethernet ch cha hai a ch MAC, vng typefield, mt vng CRC v cc thng tin lp network. Trong khi , header ca IP c cha vng timeto-live (TTL) c gn bi router ngun v b tr dn mi khi qua mt router. Bng cch loi b nhng gi tin c TTL=0, router s ngn nga cc gi tin tn ti qu lu trong h thng mng. Khng ging nh IP, Ethernet khng c vng TTL. V vy, sau khi mt frame bt u b lp, frame s c chuyn bt tn cho n khi no mt switch b tt i hoc mt kt ni l b ngt. Bridge-ID Gii thut spanning-tree c nh ngha trong IEEE 802.1D. Cc thng s c dng bi gii thut bao gm Bridge-ID s c kho st trong phn ny. Gii thut spanning-tree da trn mt s thng s ra quyt nh. Thng s bridge-ID l thng s u tin c dng bi STP tm ra trung tm ca mng, cn gi l root-bridge. Thng s bridge-UD l mt gi tr 8-bytes bao gm hai vng gi tr. Gi tr u tin l gi tr thp phn c di 2-bytes gi l Bridge-Priority v gi tr tip theo l a ch MAC 6 bytes. Bridge Priority c dng ch ra u tin ca mt bridge trong gii thut spanning-tree. Cc gi tr c th l t 0 cho n 65535. Gi tr mc nh l 32,768. Gi tr MAC trong BID l mt trong nhng MAC-address ca switch. Hai thng s BID khng th no bng nhau, bi v Catalyst switch c gn nhng gi tr MAC address khc nhau. Trong cc gii thut ca spanning-tree, khi so snh hai gi tr ca switch, gi tr thp hn lun c dng. Path cost Path cost l thng s th hai c dng bi gii thut ca spanning-tree xc nh ng i v root. c t IEEE 802.1D ban u nh ngha cost c gi tr bng 10 ly tha 9 chia cho bng thng ca kt ni tnh theo Mbps. V d ng 10M s c cost l 100 (1000/10) v ng 100Mbps s c cost l 10. Tuy nhin, do cng ngh pht trin, c cc cng ngh mi c tc cao hn c 1Gbps nn cn nh ngha li cng thc tnh cost. Cost c lu nh mt gi tr s nguyn. Thng s path cost s o lng cc bridge s gn nhau nh th no. Path cost l tng ca cc chi ph trn ng link gia hai bridge. i lng ny khng o bng hop count. Hop count cho ng i A c th ln hn hop-count cho ng i B, trong khi , nu xt theo cost, ng i qua path A s nh hn ng i qua path B. Thng s path cost c dng bi cc switch xc nh ng i tt nht v RootBridge. Gi tr thp nht ca ng i s l ng i tt nht v root-bridge.
Port-ID Thng s PortID l thng s th ba c dng bi spanning-tree xc nh ng i v root-bridge. Gi tr port-ID l gi tr 2-bytes bao gm mt hai ch s. Ch s u tin gi l port Priority, gi tr th hai c gi l port-number. Trn mt CatOS, gi tr u tin l 6bits v gi tr th hai l 10 bits. Trn IOSbased switch, c hai gi tr l 8 bits. Ta khng nn nhm ln gia PortID vI gi tr Port Number. Gi tr port number ch l mt phn ca PortID. Gi tr PortID cng thp th c u tin hn gi tr portID cao trong cc quyt nh ca STP. Hai gi tr PortID khng th no bng nhau, bi v PortNumber s ch ra switchport trn Catalyst switch. Gi tr port priority l mt thng s STP c th thay i c. Tm gi tr ca n l t 0 cho n 255 trn IOS-based switch, gi tr mc nh l 128. -----------------------------------------------
Bi 5:Redistribution 1. nh ngha
Route redistribution
Trng hp nu mt mng ca cng ty chy nhiu giao thc nh tuyn th cn phi c mt phng thc chia s thng tin nh tuyn gia cc giao thc khc nhau . Qu trnh gi l redistribution. Ch l trong trng hp tn ti nhiu giao thc nh tuyn trn cng mt router khng c ngha l redistribution t xy ra. M qu trnh redistribution ny xy ra th ta phi cu hnh chng. Trng hp c nhiu giao thc nh tuyn tn ti trn cng mt router m khng c cu hnh redistribution c gi l ships in the night (SIN) routing. C ngha l router ch trao i thng tin nh tuyn vi neighbor ca n trong cng process domain. Mc d SIN routing thng c cp ti trng hp nhiu giao thc nh tuyn trn cng mt router (nh l OSPF ca giao thc IP v NLSP ca giao thc IPX). Mt ch na l redistribution ch c th xy ra gia cc giao thc nh tuyn tng ng vi cng mt giao thc lp 3 (IP, IPX hay Apple Talk). Mt vi giao thc nh tuyn th t ng redistribution m khng cn phi cu hnh, tuy nhin thng l ta phi cu hnh th qu trnh redistribution mi din ra. Hnh 3.1 di y s miu t chnh sch redistribution ca tng giao thc nh tuyn.
Routing Protocol & Chnh sch redistribution (Redistribution Policy) Static: Phi cu hnh bng tay vo cc giao thc nh tuyn khc. Connected: Tr phi c cu lnh Network cho qu trnh nh tuyn, phi yu cu cu hnh redistribution bng tay vo cc giao thc nh tuyn khc. RIP: Yu cu cu hnh redistribution bng tay. IGRP: N s t ng din ra gia IGRP v EIGRP nu gi tr AS autonomous system ca chng ging nhau. Trng hp cn li yu cu phi cu hnh bng tay. EIGRP: N s t ng din ra gia IGRP v EIGRP nu gi tr autonomous system ca chng ging nhau. EIGRP cho giao thc Apple Talk s t ng redistribution gia EIGRP v RTMP. EIGRP cho IPX s t ng redistribution gia EIGRP v IPX RIP/SAP. Trng hp cn li yu cu phi cu hnh bng tay. Trong cc phin bn sau, NLSP c th redistribution bng tay. OSPF: Yu cu phi cu hnh redistribution gia cc OSPF process khc nhau v vi giao thc nh tuyn khc. IS-IS: Yu cu phi cu hnh bng tay gia cc giao thc nh tuyn khc nhau. BGP: Yu cu phi cu hnh bng tay gia cc giao thc nh tuyn khc nhau. Cc trng hp dn ti tn ti nhiu giao thc nh tuyn trong cng mt t chc: T chc chuyn t mt giao thc ny sang mt giao thc khc bi v h cn mt giao thc nh tuyn phc tp hn. V d chuyn t RIP sang OSPF. Do yu t lch s, t chc c rt nhiu mng con. Cng ty cn c thit k chuyn sang mt giao thc duy nht trong tng lai. V d hin ti va chy RIP, IGRP. Mong mun chuyn sang EIGRP. Mt vi doanh nghip s dng gii php host-based yu cu nhiu giao thc nh tuyn. V d, v d mt UNIX host s dng RIP khm ph gateway. Sau khi 2 cng ty c hp nht.
V mt chnh tr, c nhng t tng khc nhau gia cc nh qan tr mng khc nhau.
Trong mt mi trng rt ln, nhng vng khc nhau c nhng yu cu khc nhau, do mt gii php n l l khng hiu qu. V d: mt mng a quc gia, th EIGRP l giao thc nh tuyn c s dng access layer v distribution layer nhng BGP l giao thc nh tuyn c dng kt ni vi core layer. 2. Cc vn pht sinh v gii php khi thc hin redistribution. c trng ca cc giao thc nh tuyn m hu ht c mang trong redistribution l s khc nhau trong metric v administrative distance, v kh nng classful hay classless ca chng. Nu khng xem xt cn thn s khc nhau ny khi redistribution cc giao thc nh tuyn c th dn ti cc vn nh khng trao i mt vi hoc tt c cc tuyn (route), routing loop v black hole. a/ Metric Static route khng c metric i km vi chng, nhng mi OSPF route (tuyn OSPF) phi c mt gi tr cost i km. Mt v d khc lin quan n metric na l redistribution ca RIP route (tuyn RIP) vo IGRP. Metric ca RIP l hop count, trong khi IGRP s dng bandwidth v delay. Metric ca IGRP l mt s 24 bit trong khi ca RIP gi tr gii hn l 15. Trong c 2 trng hp, yu cu i vi giao thc nh tuyn tham gia redistribution l i vi nhng tuyn (route) c redistribution vo domain ca n th n phi kt hp c metric ca n vi metric ca nhng tuyn . Do cn c mt gii php. l khi router thc hin redistribution phi gn mt gi tr metric cho nhng tuyn tham gia redistribution, tc l chuyn i metric ca cc tuyn t giao thc c (v d l RIP dng hop count) sang giao thc mi (v d l IGRP dng bandwidth+ delay). Qu trnh chuyn i nn thc hin ngay trong lc redistribution v trn router chy nhiu routing protocol. Mt v d l EIGRP v OSPF. EIGRP c redistribution vo OSPF v ngc li OSPF c redistribution vo EIGRP. OSPF khng hiu metric t hp ca EIGRP v EIGRP cng khng hiu cost ca OSPF. Kt qu l, cc phn ca qu trnh redistribution cc router phi c gn mt cost cho mi EIGRP route trc khi tuyn c qung b sang OSPF domain. Tng t nh vy, router cng phi gn mt cp gi tr sau: bandwidth, delay, reliability, load v MTU cho mi OSPF route trc khi n c qung b sang EIGRP domain. Nu qu trnh gn metric l khng ng th qu trnh redistribution s tht bi. b. Khong cch qun l (Administrative Distance) Tnh a dng ca metric cn gy ra vn sau: nu mt router chy nhiu hn mt giao thc nh tuyn v hc mt tuyn (route) ti cng mt ch t mi giao thc tng ng, th tuyn no s c chn? Mi giao thc nh tuyn s
dng metric ca n xc nh ra route tt nht theo cch ca mnh. So snh tuyn (route) vi metric khc nhau chng hn: hop count v cost, chng khc no so snh to v cam. C mt gii php gii quyt vn ny l administrative distance. ng nh metric c gn cho mi tuyn (route) n mc u tin ca mi route c th c xc nh, administrative distance c gn cho tuyn ngun (route source) n mc u tin hn ca tuyn ngun c xc nh. Nh trong phn hai gii thiu administrative distance n nh l thc o v tin cy. Gi tr administrative distance cng nh th tin cy ca thng tin nh tuyn trao i bi giao thc tng ng cng ln. V d, gi s mt router chy 2 giao thc nh tuyn l RIP v EIGRP. Khi router hc mt tuyn ti mng 192.168.5.0 bng c 2 giao thc nh tuyn th n s nhn c thng tin v tuyn ti mng 192.168.5.0 t c RIP neighbor v EIGRP neighbor. Bi v EIGRP s dng metric t hp cho nn nhng thng tin nh tuyn hc c t EIGRP s chnh xc hn l thng tin nh tuyn hc c t RIP. Do , EIGRP tin cy hn RIP. Bng 3.3 cho bit cc gi tr administrative distance mc nh ca cc giao thc nh tuyn khc nhau. EIGRP c administrative distance l 90 trong khi RIP l 120. iu chng t EIGRP tin cy hn RIP. c. Redistributing t Classless vo Classful Protocols S suy xt thn trng c ni r c ni r khi thc hin redistribution t mt classless routing process domain vo mt classful domain. hiu c ti sao li nh vy, u tin cn hiu mt classful routing protocol phn ng li nh th no vi s thay i ca subnet. Nh bit RIP l mt classful routing protocol cho nn n khng gi mask trong thng tin nh tuyn. i vi cc route m mt classful router nhn c s rI vo mt trong 2 kh nng sau: Router s c mt hay nhiu hn interface gn vi mng chnh (major network). Router s khng c interface gn vo mng chnh.
Gii php 1: cho vic redistribution gia classful routing protocol v classless routing protocol l s dng nh tuyn tnh phn phi cc route vo trong classful routing domain. Gai php 2: thc hin route summary nhm cc subnet con thnh mt subnet to hn m classful routing domain hiu c.
Bi 6: Tho lun cc vn v cp quang Hi: 1. Cho em hi v s khc nhau gia cp quang SM v MM? 2. Cc thit b u cui hn si cp quang trc khi gn n vo switch. Trn mt s switch, em thy c giao tip FX; i khi em thy giao tip cp quang l SX hoc LX. Vy ttrong ttrng hp no th mnh s dng fx, v trong trng hp no mnh dng sx. Si cp patch-cable dng cho fx l st/sc. Tuy nhin em khng phn bit c trong trng hp no em dnng st/st hoc sc/sc. Cc anh c th gii thch cho em c khng? 3. Cc bn th l gii ti sao si n mode cn n cc b suy hao 5dB, 10dB khong cch gn? Tr li: 1. Si quang l nhng dy nh v do truyn cc nh sng nhn thy c v cc tia hng ngoi. Chng c 3 lp: li (core), o (cladding) v v bc (coating). nh sng c th phn x mt cch hon ton trong li th chit sut ca li ln hn chit sut ca o mt cht. V bc pha ngoi o bo v si quang khi b m v n mn, ng thi chng xuyn m vi cc si i bn cnh. Li v o c lm bng thu tinh hay cht do (Silica), cht do, kim loi, fluor, si quang kt tinh). Thnh phn li v v c chic sut khc nhau. Chit sut ca nhng lp ny nh th ny s quyt nh tnh cht ca si quang. Chng c phn loi thnh cc loi si quang n mode (Single Mode SM) v a mode (Multimode -MM) tng ng vi s lng mode ca nh sng truyn qua si quang. Mode sng l mt trng thi truyn n nh ca sng nh sng (cng c th hiu mt mode l mt tia). Si quang n mode hay si quang a mode u ch truyn mt tn hiu (l d liu m ta cn truyn). Mun truyn nhiu d liu t cc knh khc nhau, ta phi dng n cng ngh WDM (truyn nhiu bc sng trn cng mt si quang). Si a mode c th truyn cng lc nhiu nh sng vi gc anpha khc nhau, cn si n mode ch c th truyn 1 nh sng vi 1 bc sng nht nh. Do si quang l vt liu truyn thng tin da trn nh lut phn x nh sng. Tia sng khi i t mi trng c chit sut cao qua mi trng chit sut thp th khng i thng (hay cn gi l tn x) m s phn x li. Do , khi nh sng mang thng tin, s c truyn i m khng b suy hao g c (v n c chy lng vng trong , phn x bn ny, ri phn x bn kia. Si quang n mode th li c chit sut l mt hng s v chit sut ca v cng l 1 hng s. Khi nh sng s truyn i theo ng ziczac trong si quang ( lnh pha ca tn hiu khi s ng k). Si a mode l cng ngh tin tin hn, chit sut t li ra n v s gim t t (nhng vn m bo mt t s chit sut
nh sng ch phn x ch khng tn x), khi th nh sng s i theo ng cong, lnh pha s t hn nhiu so vi hnh ziczac ca loi n mode. a mode cn chia lm 2 loi, l step mode v grade mode. Step mode th chit sut t li n v gim dn, nhng theo tng nc, cn grade mode th gim lin tc v d nhin l grade mode s tt hn step mode. D nhin l vic dng a mode th cn ph thuc nhiu yu t na nh l gi thnh, cc thit b u cui (ghp knh quang). Si SM ch truyn c mt mode sng do ng knh li rt nh (khong 10 micromet). Do ch truyn mt mode sng nn SM khng b nh hng bi hin tng tn sc v thc t SM thng c s dng hn so vi MM. Si MM c ng knh li ln hn SM (khong 6-8 ln), c th truyn c nhiu mode sng trong li. Thng s vt l ca hai loi cp ny: ng knh li si (phn truyn tin): Core. SM: 9/125; MM: 50/125 v 62.5/125. ng knh v phn x: Cladding th c SM v MM u nh nhau l 125um. Hin nay, cp quang single mode ch dng cho ng trc, ngoi vic gi thnh ra, cng ngh ca cp single mode rt khc khe, v rt kh trong vic thi cng cng nh s dng. L do chnh l do lp li ca cp single mode rt nh (khoang 27 Micromet) cn ca multi mode thi ln hn rt nhiu (khong 130 Micromet). Ngoi ra, do kt cu li single mode cho nh sng i theo ng thng, m gi thnh ch to, cng nh chnh xc trong thi cng, thit b cng ngh cao lm cho cp SM kh thc hin trong cc cng trnh dn s. V Coating th ty thuc vo dc tnh cn bo v m ngi ta lm lp ny, tuy nhin thng thng i vi cp out door th n l 250, vi cp indoor th n l 900, iu ny khng ph thuc vo cp SM hay MM. V s dng th ty thuc vo cng sut pht, nhy thu, khong cch truyn dn, tc yu cu v gi thnh m ngi ta quyt nh dng SM hoc MM. Minh ha hnh ng i ca nh sng truyn trong li (m nguyn nhn l do kt cu ca li Single Mode Multi Mode: =================== - - - >- - - - >- - ng nh sng =================== Single Mode
=================== /\/\/\/\/\/\/\/\/\ - - - - - - - - - ng nh sng \/\/\/\/\/\/\/\/\/ =================== Multi mode Tip cn theo quang hc tia (ray optic), mode ca si quang c hiu l mt tia sng nh sng n sc. Si quang a mode l si quang truyn nhiu tia sng cng mt lc, trong khi si quang n mode ch truyn duy nht mt mode dc trc. Tip cn theo quang hc lng t, nh sng l mt loi sng in t (hai thnh phn E, H) v truyn dn ca n trong si quang phi tun th cc phng trnh ca nh lut Maxoen. Ngi ta nhn thy rng thnh phn in (vc t E) v thnh phn t (vc t H) ti li v v ca si quang khng c lp vi nhau m c mi lin h thng qua iu kin bin li-v. Bt c cp nghim no ca h phng trnh Maxoen li v v tho mn iu kin bin c gi l mt mode truyn sng. Ngoi cch phn loi nh trn, cn vi cch phn loi cp quang khc. Theo Mode th c: SM v MM (MM c 2 loi: 62.5 v 50). Theo mi trng lp t th c Outdoor v In door. Outdoor li chia ra thnh cc loi: F8 v Underground. 2. Ti sao si quang n mode c kh nng truyn tt hn si a mode? Si n mode truyn xa v tt hn si a mode.Trong Single mode, nh sng i theo gn nh mt ng thng trng vi trc cp, cn trong Multi Mode, nh sng i theo mt chm tia sng c dng hnh sin ng trc (v th m ta c th ghp thm nhiu nh sng c cc bc sng khc nhau). Si quang a mode s gp hin tng tn sc trong si quang gia cc mode truyn dn. y l yu im chnh ca a mode so vi n mode. Do m tn hiu trong si quang a mode d b tn x hn, tc truyn km hn v khong cch truyn gn hn. Si quang c ch s bc v ch s lp tu theo hnh dng v chit sut ca cc phn ca li si. Si quang n mode hay a mode ph thuc vo bc sng ca nh sng truyn trong . Cng mt si quang nhng n c th l si n mode vi bc sng nay v l si a mode vi bc sng khc. Tuy nhin trong si quang, ngi ta ch truyn mt s bc sng nht nh. Nhng bc sng ny gi l cc ca s quang. Ba bc sng l 850nm, 1330nm, 1550nm. Thng th bc sng 850nm t c dng. MM c cc bc sng chun l: 780, 850 v 1300. Hin nay cc thit b t dng bc sng 780. SM c cc bc sng: 1310, 1550, 1627. Cc thit b SM dng cng ngh DWM th cn c th s dng nhiu bc sng khc na. Do khi nim si a mode v n mode phi gn lin vi bc sng truyn. Khong cch truyn (theo
khuyn co) ca cp a mode l 500m. Khong cch truyn (theo khuyn co) ca cp n mode l 3000m. Si quang n mode c dng ch yu do ko c hin tng tn sc gia cc mode l nguyn nhn ch yu gy nhiu si quang. Si n mode c dng lm mng backbone cn si a mode ch dng truyn gia cc mng trong vng. Thm na c n mode v a mode u dng nh sng laser hoc led c, cn s dng ci no l tu vo tng trng hp c th do nhu cu v yu cu ca mng. Khi truyn trong si quang, sng nh sng b chi phi bi mt s hin tng sau: (*) Suy gim (attenuation): Suy gim trong si quang do hai nguyn nhn chnh, l hp th ca vt liu v tn x ReyLeng. Hp th vt liu nh hn tn x ReyLeng nn c th b qua. Tn x ReyLeng do cc thng ging vi sai trong cu trc vt liu, v gim khi bc sng tng. th tng hp ca cc nguyn nhn suy gim gip tm ra ba ca s truyn sng s dng rng ri ngy nay (800nm, 1300nm v 1550nm) (*) Tn sc (dispersion): Tn sc l hin tng cc thnh phn khc nhau ca tn hiu cn truyn truyn i vi cc tc khc nhau trong si quang. Tn sc do gy ra hin tng gin xung nh sng u ra, gy ra nhiu chng ph v l nguyn nhn chnh dn n hn ch ca khong cch truyn trong si quang ngy nay. C mt s loi tn sc khc nhau, gm tn sc mode (si quang a mode mi c), tn sc phn cc v tn sc n sc (gm tn sc vt liu + tn sc ng dn sng), mi loi c mt nh hng khc nhau n qu trnh truyn ca tn hiu. Cc loi si quang dch tn sc hn ch c mt phn vn ny nn c khong cch truyn xa (longhaul). (*) Cc hiu ng phi tuyn: Khi truyn nhiu mode trong si quang, hin tng phi tuyn gy ra hin tng sinh ra cc hi t cc mode truyn c bn, dn n nhiu ti u thu v gim cng sut tn hiu truyn. Cc hin tng ny c nh hng cng r rt khong cch cng ln, v khong cch cng khng phi l tham s duy nht. Chng lm nh hng tiu cc n bin , tn s, cc tham s khc v xung truyn, v do nh hng n kh nng nhn dng ca u thu. Hn na, cc nh hng ny li khng ging nhau, v d b khuych i c th dng hn ch vn attenuation, nhng v hiu vi gin xung, v cc b ti to xung khng th m bo cng sut ngng ca u thugy ra nhiu kh khn trong khc phc Trong s cc nh hng th tn sc l nghim trng nht, v trong s cc loi tn sc th tn sc mode l ng k nht. Hy tng tng hai mode sng li v ngoi nht. Khong cch v thi gian khi n ch ca chng l yu t quyt nh n khong cch truyn. Thng thng khong cch ny khng c vt qu 1/2 chu k xung cn truyn b thu c kh nng hi phc tn hiu nh c. l l do chnh si n mode truyn tt hn si a mode trn cc tham s k thut chung. Ngoi ra, cn rt nhiu vn nu mun thc s
hiu c vn mode v phn bit gia chng. Truyn dn quang vi power budget l bi ton cn phi cn thn khi tnh ton thit k. Ngy nay, cng ngh WDM v cc pht hin mi trong k thut quang v ang hng th h mng n mt k nguyn mi, k nguyn ca Optical Internet. ng knh li ca si quang n mode nh hn ng knh li ca si quang a mode. iu ny xut pht t iu kin m bo tnh n mode ca si quang cho bi cng thc sau: (2*PI/lamda)*a*sqr(n1*n1-n2*n2) 128K th khch hng dngloi no cng c min l > 128K.Thng tt c cc loi thit b ny c mt u l V.35, cn mt u kia ni vo ng line cp ng ko t bu in. TimePlex AD3 c cp trn ngng sn xut v c thay th bng TimePlex SYNCHRONY AD7 v hin ti l AD-10/FR2. Hng cung cp NTU th nhiu lm, vn l bn c bu in khuyn co s dng loi g tng thch. DDN l 1 network hon chnh dng cung cp cc dch v v data. Hin ti mng DDN s dng cng ngh ghp knh TDM (TDM-based). Trong tng lai c l s chuyn dn sang cc cng ngh mi nh DPT/RPR hoc chuyn sang ATM-based, IP-based. Mng DDN l mt tp hp cc access node (s dng cc b mini MUX, DACS ) dng mng truyn dn ni tnh hin c kt ni cc access node li vi nhau (ci nh ngha ny khng chc lm . Theo em th DDN (Digital Data Network) l mt h thng mng ch da trn truyn dn cp
ng. Hin nay mng ca bu in l mng DDN (tt nhin l backbone th vn l Optical ri) Cc access node c 2 nhim v: 1. Cung cp dch v data ti ngi dng cui. v d nh dch v leasedline. 2. Tp trung lu lng (multiplexer) truyn i trn mng truyn dn. Di y so snh Leased lines (LL) vi mt s cng ngh khc nh FrameRelay v MPLS/VPN. Vic chn LL hay FrameRelay ty thuc ch yu vo nhu cu s dng. Sau y l bng so snh 1 cch c bn nht: LL: bo mt cao nht v c ng truyn dnh ring. Thch hp cho cc ng dng rt quan trng hay cc ng dng i hi cao, khng chp nhn delay (nh VoIP, SAP,). Khng ph thuc vo kh nng v trnh k thut ca nh cung cp dch v, v LL hat ng lp 1 chi ph rt cao FrameRelay: bo mt thp hn v mng FR, d liu c truyn i chung vi cc d liu ca nhng khch hng khc. Thch hp cho cc ng dng khng i hi cao. Ph thuc vo kh nng v trnh k thut ca nh cung cp dch v, v FR hat ng lp 2 chi ph r hn LL rt nhiu So snh gia leased line (TDM) v MegaWAN (VPN/MPLS), gi s tc ng truyn cn thu nh nhau. Kt ni 1 vn phng v 2 chi nhnh. Leased line: u im: - Bng thng m bo 100% - Delay nh - Jitter nh - a dch v (c th s dng cho cc dch v non-IP v IP). Khuyt im: - Gi thu rt t. - Thit b u cui rt t, t thng dng, kh tm. - Buc phi s dng 1 cp thit b cho mi knh > vn phng cn 2 thit b phc v cho 2 im chi nhnh. MegaWAN: u im: - Bng thng m bo (ch s n khng khai CBR -Constant Bit Rate cho bc thi). - Gi thu rt r - Thit b u cui thng dng, d mua (modem ADSL bnh thng hoc
SHDSL). HDSL v G.shdsl cho cc kt ni data 128Kbps< n x 64Kbps 200m (cch con ng). ni gia 2 building, cty dng cp quang (cch ny hp l nht cha?) ni 2 u. 2 u s dng LAN router cisco 26xx ( tch ri 2 mng LAN) ch c 2 port FE 10/100. Vy by gi dng cch no ni c cp quang vo ci u Rj-45 ca router? Nu ni thng vo Switch 29xx c u cho cp quang 2 u building th c th tch ri 2 mng khng? Rt cm n Tr li t cc thnh vin din n: Nu mun ni 2 vn phng vi khong cch gn (=< 3km) c rt nhiu gii php ph thuc vo cc thit b u cui m cng ty cc bn ang c: 1. Cp ng cng ngh G.SHDSL hay cng ngh VDSL: C th kt ni hai ta nh bng dy cp ng (loi cp in thoi). Dng thit b hai u VC102 (Planet VDSL Converter). * Thit b ny c nhiu ch la chn * Khong cch ti a 1km2 * Bng thng khong 11mb * Gi cng khong hn 800usd cho 1 cp. Thit b cn thit l hai modem s dng cng ngh trn c port Lan (1 hoc 4 port)
vd: Loi modem G.SHDSL Paradyn 1740 A2 gi tm 500usd, Zyxel P 792H gi tm 400usd. Loi modem VDSL Zyxel P972. Nu dng cp ng cng ngh G.SHDSL v mun u vo Router: cc bn mua cc loi NTU ang c trn th trng c Interface V35 l ok, tc Syn 2Mbps. Lc ny mng ca bn ging nh mt Wan kt ni hai LAN. Nu cng ty d d th mua Interface E1 (modem v c Router). vd: sn phm ca Telindus, CTC Lu : bn phi c chc nng ko c cp ng nu ngoi ng, trong khun vin cng ty th min bn. 2. Cp quang: kt ni bng cp quang bn cn c: - Cp quang: nn xi loi outdoor, c armoured cng tt. Vi khong cch khong 200-500m th dng cp multimode 50/125um l tt nht. S core th ty bn nhng ti thiu l 2 core (Tx & Rx), thng thng l 4 hoc 8 core d phng. - ODF x 2 pcs cho 2 building:Ty v tr u ni/ phng thit b bn c th chn loi rack mount hoc wall mount, FO adapter chn loi thng dng nh ST hoc SC - Connector quang: ti thiu l 4 (2 cho mi u), c th chn ST hay SC cho thng dng cng nh d hn u v phi cng loi vi adapter ca ODF - Patch cord quang: ni t ODF sang media converter, di khong 3m l . Ch 2 u connector phi cng loi vi adapter ca ODF v FO connector ca media converter. - Media converter:ty nhu cu bng thng gia 2 building bn c th chn FE hoc GE. Ch cc thng s: Cng sut pht ti thiu, Cng sut pht ti a, nhy u thu, ngng cng sut thu ti a, kiu FO connector. - Cui cng l 2 si patch cord RJ45 ni t media converter ti switch. Dng Media Converter l hay nht v gi r nht. Trn th trng c nhiu loi cc bn c th d gi c gi tt nht. hai u ca ng cp quang cc bn c th dng switch layer 2 hoc dng router hoc mt bn l switch v mt bn l router. Bn kt ni hai switch bng cp quang th hai mng LAN tr thnh mt nu bn khng cu hnh VLAN. u kia ni thng vo switch L2. Trang b 01 Switch c 02 cng cp quang l n. Mng chy thoi mi 1000Mbps. RJ45 cp quang (LAN)[SWITCH c cng cp quang] -[SWITCH c cng cp quang]-(LAN) Nu dng cp quang v mun u vo Router hai u: Cc bn c th dng modem quang. Trn Modem quang c nhiu la chn hn v n ra nhiu
Interface hn : LAN, E1 v V35. Nu bn mun dng cp quang trc tip trn router bn c th mua them module NM-1FE-FX. Nu khng mun u t thm switch c cng quang bn c th s dng Converter ca hng Planet Fast Ethernet Media Converters. Hin nay trn th trng c cc dng media converter 100base FX/100base TX ca Plannet. Gi r (t 100-300$ ty loi). Dng cp Munltimode th media converter r hn Single Mode, khong cch t 500m->80km. Thit b ny c th cho bng thng l 100Mbps, khong cch 2km vi multimode v khong 35 km vi cp singlemode. S dng 01 cp converter l n nht, gi c cng bnh thng m u im nht vn l d lp t v s dng, khai thc. Gii php cp quang rt tt nhng chi ph cao cho m hnh mng cho 2 ta nh ch cch nhau 200m. Dng cp quang l gii php c bng thng cao v n nh nht, ko b nh hng bi mi trng nh wireless bridge. Tuy nhin chi ph c th cao hn cng nh thi cng s rc ri hn. Vi khong cch trn 2 Km th bn dng cp quang n mt. Tc ca ng kt ni lc ny khng ph thuc vo cp quang m ch ph thuc vo thit b u cui (router/switch) ca bn. Bn chy c tc Gb bnh thng hoc thm ch 10Gb. Khong cch 200m th khng nn dng cp 50/125 m dng cp 62.5/125 th n hn. V mt l thuyt th cp quang 50/125 c suy hao t hn cp 62.5/125 nn cp 50 c dng cho c ly xa hn, tuy nhin hin nay cng sut pht quang ca thit b c ci thin ng k v gi thnh cng gim nhiu ri. L do nn dng cp 62.5/125 v loi ny rt ph thng v c nhiu nh cung cp nn bn c th mua c cc ph kin i km nh dy ni, dy nhy mt cch d dng v gi thnh cng r, chc bn bit gi thnh SP VN khng ph thuc nhiu vo gi SX m ch yu ph thuc vo c bao nhiu ngui bn thi. Mt iu na l hin nay VN vn s dng kiu bm u cp quang m t khi hn, kiu bm u gi thnh va t m li khng linh hot khi cn thay i. Sau cng, vn cn gii php Wireless. Bn c th ch cn dng 1AP cho c ly 200m xy dng 1 wireless Lan. Lc ny anh cn thm cc wireless card cho cc client. khong cch ln hn,anh cn dng 2 AP bridge thit lp 1 point to-point connection. Khi ny anh vn c 1 LAN duy nht. Trong gii php ny khng cn n cc wireless card, t PC n bridge ta s dng UTP. Chc nng ca AP l kt ni hai LAN vi nhau.
Bi 9:
Khi phc mt khu cho router Ciscot vn : Khi cu hnh mt router, ngi qun tr thit b thng t cc mt khu ngn chn vic ng nhp khng hp l vo thit b do mnh qun l. V d, ngn chn vic ng nhp vo mode privileged t i n cc mode cu hnh su hn bn trong, ngi qun tr c th s dng enable password hoc enable secret: Router(config)#enable password vnpro (cu hnh enable pasword l vnpro) Router(config)#enable secret cisco (cu hnh enable secret l cisco) Hoc thm ch c th t mt khu ngn chn ng nhp khng hp l ngay t cng console: Router(config)#line console 0 Router(config-line)#password vnpro Router(config-line)#login Vic t cc mt khu nh vy l cn thit nhm m bo mt mc bo mt c bn nht cho thit b. Tuy nhin, i lc v bt cn, ngi qun tr c th nh nhm mt vi k t khi khai bo mt khu hoc c th qun mt mt khu ng nhp do khng ng nhp c vo thit b do mnh qun l. Trong trng hp ny, ngi qun tr cn phi thc hin mt s thao tc nhm khi phc li mt khu cho thit b. Bi vit ny s trnh by nguyn l c bn c s dng khi phc mt khu cho cc router ca tp on Cisco, km theo l s hng dn c th cc thao tc khi phc mt khu trn cc dng router Cisco ph bin hin nay l cc dng 2600, 2800. Nguyn l c bn: Vic khi phc mt khu da trn vic can thip vo bc cui cng ca tin trnh khi ng ca router. can thip vo tin trnh ny, ngi qun tr phi thc hin thay i gi tr ca mt thng s k thut trn router c tn gi l thanh ghi cu hnh (configuration register). Thanh ghi ny bao gm mt chui nh phn 16 bit vi mi bit u mang mt ngha, chc nng ring. Thit lp cc gi tr 0 hay 1 cho cc bit c th nh hng n tin trnh khi ng ca router. Thanh ghi cu hnh thng c hin th di dng s hexa (h m 16), v d; 0x2102, 0x2142, 0x2100,.v.v ( k hiu 0x c s dng ch ra y l cc s hexa). Ta xem xt tin trnh khi ng ca router:
1. POST (Power On Self Test): y l bc u tin, din ra ngay sau khi bt ngun ca router, quy trnh POST s kim tra ton b phn cng ca router m bo cc phn cng hot ng ng. 2. Np chng trnh bootstrap t ROM vo RAM chy, chng trnh ny chu trch nhim thc hin quy trnh np h iu hnh (IOS) cho router. 3. Np IOS (h iu hnh ca router) t b nh Flash vo RAM chy. 4. Sau khi c np, IOS s np file cu hnh startup-config t b nh NVRAM vo b nh RAM thnh file running-config v thc hin file cu hnh ny. Tt c cc mt khu sau khi khai bo u c lu li trong file cu hnh startup-config trn b nh NVRAM v v th sau khi file ny c np v chy th cc mt khu s pht huy tc dng. Do , b qua cc mt khu th phi iu khin router b qua file startup-config trong bc ny v np vo mt cu hnh trng. S dng cu hnh trng v vo c cc mode cu hnh su hn, c th chnh sa hoc xa b cc mt khu lu trong file cu hnh c, t c th s dng li file cu hnh c trong ln khi ng tip theo nhng vi cc mt khu c sa li theo ca ngi qun tr. thc hin c vic ny, cn phi thit lp gi tr l 1 cho bit th 6 ca thanh ghi cu hnh (tnh t phi sang tri, bit u tin ng ngoi cng bn phi c s th t l 0). Gi tr ca c thanh ghi khi thit lp gi tr 1 cho bit s 6 thng c dng l : 0x2142 , c ngha b qua startup-config trong NVRAM khi khi ng. Bnh thng, thanh ghi ny c gi tr mc nh l 0x2102 (trong bit s 6 bng 0 c ngha: s dng file startup-config trong NVRAM). Cc bc c th khi phc mt khu trn router Cisco cc dng 2600, 2800: u tin, gi thit router b cu hnh sai mt khu hoc mt khu b qun dn n ng nhp thit b khng thnh cng:
Ta tin hnh cc bc nh sau khi phc mt khu cho router: 1. Tt cng tc router v sau khong 30s th bt tr li, khi router khi ng, mn hnh s hin th cc dng sau:
( Nhn Ctrl + Break ti y) 2. Ctrl + Break l t hp phm ngt c tc dng a router vo mt ch c bit gi l ch rommon. Ti ch rommon, router s dng h iu hnh ph trong b nh ROM chy ch khng s dng h iu hnh chnh IOS trong flash chy:
L : Nhn Ctrl + Break ngay khi bt router c th lm ng router. Tt nht l ch nhn ngt khi router hin thng bo v kch thc b nh chnh. Ta cng c th nhn Ctrl +Break trong 15 giy u tin. Lu rng i vi cc chng trnh terminal khc nhau, t hp phm ngt c th khc nhau. Chng trnh terminal ph bin nht l Window Hyper Terminal s dng t hp phm Ctrl+Break ngt. 3. Ti rommon, ta thc hin lnh i gi tr ca thanh ghi cu hnh thnh 0x2142.
4. Sau khi i xong gi tr ca thanh ghi cu hnh, phi khi ng li router. Trong rommon, lnh khi ng li router l lnh reset.
5. Sau khi khi ng li, router sau khi np xong IOS, s b qua khng np cu hnh t NVRAM chy na m i vo mode setup, cho php ta s dng mt cu hnh trng chy.
Ta nhp phn tr li l no s dng cu hnh trng. Khi s dng cu hnh trng, ta i vo c mode privileged ca router, t c th tip tc i vo cc mode cu hnh su hn chnh sa hoc loi b mt khu trong file cu hnh c.
6. Tip theo, copy file startup-config vo thnh file running-config. Sau khi copy file startup-config vo, ta c th thay i chnh sa li mt khu c nm trn file ny.
Ta thy tn router c i t tn mc nh l Router thnh Vnpro. Nh vy, ta lm vic trn file cu hnh c v b qua c mt khu. 7. K tip, ta ch vic xem mt khu no cn chnh sa hoc loi b lm cc thao tc chnh sa, loi b tng ng. y, v d mt khu cn sa li l enable password, sa li thnh vnpro.
Sau khi sa xong, nh lu cu hnh ln cu hnh c t nay v sau s dng mt khu mi. 8. Bc cui cng, ta phi sa li thanh ghi cu hnh v mc nh nh c l 0x2102 tin trnh khi ng sau ny c din ra bnh thng.
Thanh ghi cu hnh sau khi c sa vn gi nguyn gi tr 0x2142, ta phi khi ng li router th gi tr mi 0x2102 mi c s dng. Trn y l nguyn l v cc bc dng khi phc mt khu li hoc b qun cho router cc dng 2600, 2800 ca hng Cisco. i vi cc dng khc c th c bin i cht t v cch thc v dng lnh nhng nguyn tc th vn ging nh vy, c th tham kho thm trong cc ti liu hng dn i km hoc trn trang h tr ca Cisco. ----------------------------------------------------
Bi 10: Clockrate vs bandwidth. Tng kt cc tho lun c a ra v bandwidth v clockrate Cc cu hi xung quanh vn ny: -Cu lnh clock rate to xung nhp, vy nu chng ta g clockrate cng ln th tc truyn d liu gia DCE v DTE cng cao phi khng? -Cn cu lnh Bandwidth khi g vo mt interface no th c tc dng g? - Cp xung Clockrate l dng ng b 2 u (1 l DCE trn thc t l nh cung cp dch v, 1 l DTE- l ngi s dng), nhng ng b lm g? Cn tc ng truyn l ph thuc vo Bandwidth, BW cng cao th tc ng truyn nhanh v ngc li. Clockrate nh hng n ng truyn? Nu ni nh bn th 1 ng c BW=256 vi Clockrate = 9600 v 1 ng c BW = 64 vi Clockrate = 128000 th ng no s nhanh hn. Mt s kin tr li: - Lnh bandwidth thc cht l to mt tham s u vo tnh ra composite metric (ca IGRP). khi bandwidth cng ln th metric tnh ra cng nh( nh vy con ng s c tin cy cao hn, v s c u tin so vi cc con ng khc n cng mng ch router chn update vo bng nh tuyn). Lnh ny khng c tc dng lm tng tc truyn gia DCE v DTE.
- Cn lnh clockrate, s lm thay i tc truyn d liu v xung nhp cao th d liu s c truyn vi tc cao hn. - Clock rate cng cao th d nhin s cho bn tc cng cao, nhng vi iu kin DTE v DCE phi p ng c. Hn th na tc clockrate khng phi l con s bt k bn ngh ra, ri g vo ! M n c nhng con s c nh sn, v d nh 9600,19200,56000,64000,115200, v ty thuc vo truyn sync hay async m nhng con s quy nh ny khc nhau. Nhng d sao i na th clockrate ny cng khng quyt nh hon ton tc truyn trong 1 s trng hp, th d nh modem async, frame relay, i vi modem async th clock rate ch quyt nh c tc t DTE n DCE m tc thc th ph thuc vo carier ca DCE (modem) . Cn frame relay th clock rate nh hng n access rate m thi, data truyn nhanh hay chm th cn ph thuc CIR. Nhng d sao i na th khi truyn async ta nn cho clockrate > tc carier v nh vy gip cho DTE s gip CPU trn DTE nh ti hn cho cng vic truyn c thi gian trng nhiu hn cho nhng vic khc. Clock Rate ch c ngha trong ch truyn ng b, khng c ngha trong truyn bt ng b. Trong ch truyn bt ng b, ng h xung nhp hai u khc nhau hay ni cch khc l ko ng b vi nhau th vic cp xung nhp s ko c ngha g c. Khi dng lnh clock rate, g ? s ra cc tc ph hp. Con s ny lun l bi s ca 9600 bps. - Trong truyn dn FR, CIR c ngha l tc m bo ca nh cung cp dch v cho khch hng. Trong iu kin mng b nghn th nh cung cp dch v vn m bo tc truyn = CIR m ko thp hn. Do , thng s CIR cng ko nh hng n tc truyn ca FR. - Bandwidth th c tc dng gip cc routing protocol tnh cc composite metric, khng c tc dng v vn tc trong truyn data. - Clockrate th hin tn s trn s liu c chuyn i. Tn s cng cao th s liu c chuyn i cng nhanh. Clockrate lm vic layer 1. Cn bandwidth th hon ton khng lin quan g n layer 1 c. N ch gip cho ngi qun tr theo di d dng hn. Ngai ra, bandwidth cn c mt s dynamic routing protocols nh OSPF, EIGRP dng tnh ton best route n destination. Trong v d trn th ng c clockrate 128k s nhanh hn rt nhiu so vi ng c clockrate 9.6k - Kh nng truyn s liu khng ch ph thuc vo clockrate m cn l thuc vo nhng yu t khc na nh ng kt ni vt l, cng ngh truyn dn. - Trong trng hp dng dial-up, cng ngh hin ti ch cho php n 56K. Xin lu l 56K ch l tc kt ni l thuyt. Tc thc t khi kt ni s thp hn, v d nh 48k. Lu l y khng phi l tc truyn s liu, ch l tc
thi im kt ni m thi. Trong qu trnh truyn s liu, 2 modems 2 u s lin tc trao i vi nhau v tm ra tc kt ni n nh cao nht. Ty theo ng vt l (xa hay gn, tt hay xu,..) m tc truyn s liu thc t s thay i, chng hn nh ch cn 33.6k, 19.2k hay thm ch khng th truyn c v c qu nhiu li Trong trng hp ca ADSL, cng ngh mi ny cho php truyn s liu mt tc cao hn so vi trng hp dng dial-up. Trong trng hp dng lease line, tc 128k c bo m v ng b trn ton b ng i t im A n im B. Thit b 2 u phi c kh nng h tr hat ng tc ny Tc ny s c nh v khng thay i theo thi gian. - Khi chng ta s dng router Cisco, c hai cu lnh thng dng lin quan n bng thng. Th nht l lnh clock rate, lnh ny nh ngha t l bit lp 1 thc s. Cu lnh c s dng khi router cung cp xung ng h, in hnh khi kt ni router s dng interface serial vi mt vi thit b ln cn(v d nh vi router khc). - Cu lnh bandwidth thit lp lng bng thng sn c trn interface. V d: giao thc nh tuyn EIGRP (Enhanced Interior Gateway Routing Protocol) la chn cc metric cho interface da theo cu lnh bandwidth, khng da theo cu lnh clock rate. Ni tm li, bng thng ch thay i hot ng ca cc tool trn interface nhng khng bao gi thay i tc gi bit tht s trn mt interface. - Mt s tool QoS lin quan n bng thng ca interface, c nh ngha bi cu lnh bandwidth. Cc k s nn xem xt bng thng mc nh khi cho php cc yu t QoS. i vi cc interface serial ca router Cisco, bng thng mc nh c thit lp vi tc T1 bt k bng thng thc s. Nu s dng subinterface, chng tha hng bng thng c thit lp cho interface vt l tng ng.
Bi 11:
AAA1.1.Gii thiu tng quan AAA 1.1.1.Vic s dng AAA trong v bo mt v iu khin truy cp m rng mng Cc nh qun tr mng ngy nay phi iu khin vic truy cp cng nh gim st thng tin m ngi dng u cui ang thao tc. Nhng vic lm c th a n thnh cng hay tht bi ca cng ty. Vi tng , AAA l cch thc tt nht gim st nhng g m ngi dng u cui c th lm trn
mng. Ta c th xc thc (authentication) ngi dng, cp quyn (authorization) cho ngi dng, cng nh tp hp c thng tin nh thi gian bt u hay kt thc ca ngi dng (accounting). Nh ta thy, bo mt l vn rt quan trng. Vi mc iu khin, tht d dng ci t bo mt v qun tr mng. Ta c th nh ngha cc vai tr (role) a ra cho user nhng lnh m h cn hon thnh nhim v ca h v theo di nhng thay i trong mng. Vi kh nng log li cc s kin, ta c th c nhng s iu chnh thch hp vi tng yu cu t ra.Tt c nhng thnh phn ny l cn thit duy tr tnh an ton, bo mt cho mng. Vi thng tin thu thp c, ta c th tin on vic cp nht cn thit theo thi gian. Yu cu bo mt d liu, gia tng bng thng, gim st cc vn trn mng, tt c u c th tm thy trn dch v AAA. 1.1.2. Tng quan AAA AAA [1] cho php nh qun tr mng bit c cc thng tin quan trng v tnh hnh cng nh mc an ton trong mng. N cung cp vic xc thc (authentication) ngi dng nhm bo m c th nhn dng ng ngi dng. Mt khi nhn dng ngi dng, ta c th gii hn thm quyn (authorization) m ngi dng c th lm. Khi ngi dng s dng mng, ta cng c th gim st tt c nhng g m h lm. AAA vi ba phn xc thc (authentication), cp quyn (authorization), tnh cc (accounting) l cc phn ring bit m ta c th s dng trong dch v mng, cn thit m rng v bo mt mng. AAA c th dng tp hp thng tin t nhiu thit b trn mng. Ta c th bt cc dch v AAA trn router, switch, firewall, cc thit b VPN, server, 1.1.3. nh ngha AAA Cc dch v AAA c chia thnh ba phn, xc thc (authentication), cp quyn (accounting), tnh cc (accounting). Ta s tm hiu s khc nhau ca ba phn ny v cch thc chng lm vic nh th no. iu quan trng nht l hiu v cc kiu khc nhau ca tnh cc (accounting). 1.1.3.1.Xc thc (Authentication) Xc thc dng nhn dng (identify) ngi dng. Trong sut qu trnh xc thc, username v password ca ngi dng c kim tra v i chiu vi c s d liu lu trong AAA Server. Tt nhin, ty thuc vo giao thc m AAA h tr m ha n u, t nht th cng m ha username v password. Xc thc s xc nh ngi dng l ai. V d: Ngi dng c username l vnpro v mt khu l L@bOnlin3 s l hp l v c xc thc thnh cng vi h thng. Sau khi xc thc thnh cng th ngi dng c th truy cp c vo mng. Tin trnh ny ch l mt trong cc thnh phn iu khin ngi dng vi
AAA. Mt khi username v password c chp nhn, AAA c th dng nh ngha thm quyn m ngi dng c php lm trong h thng. 1.1.3.2.Thm quyn (Authorization) Authorization cho php nh qun tr iu khin vic cp quyn trong mt khong thi gian, hay trn tng thit b, tng nhm, tng ngi dng c th hay trn tng giao thc. AAA cho php nh qun tr to ra cc thuc tnh m t cc chc nng ca ngi dng c php lm. Do , ngi dng phi c xc thc trc khi cp quyn cho ngi . AAA Authorization lm vic ging nh mt tp cc thuc tnh m t nhng g m ngi dng c xc thc c th c. V d: ngi dng vnpro sau khi xc thc thnh cng c th ch c php truy cp vo server VNLABPRO_SERVER thng qua FTP. Nhng thuc tnh ny c so snh vi thng tin cha trong c s d liu ca ngi dng v kt qu c tr v AAA xc nh kh nng cng nh gii hn thc t ca ngi . iu ny yu cu c s d liu phi giao tip lin tc vi AAA server trong sut qu trnh kt ni n thit b truy cp t xa (RAS). 1.1.3.3.Tnh cc (Accounting) Accounting cho php nh qun tr c th thu thp thng tin nh thi gian bt u, thi gian kt thc ngi dng truy cp vo h thng, cc cu lnh thc thi, thng k lu lng, vic s dng ti nguyn v sau lu tr thng tin trong h thng c s d liu quan h. Ni cch khc, accounting cho php gim st dch v v ti nguyn c ngi dng s dng. V d: thng k cho thy ngi dng c tn truy cp l vnpro truy cp vo VNLABPRO_SERVER bng giao thc FTP vi s ln l 5 ln. im chnh trong Accounting l cho php ngi qun tr gim st tch cc v tin on c dch v v vic s dng ti nguyn. Thng tin ny c th c dng tnh cc khch hng, qun l mng, kim ton s sch. -----------------------------------------------Bi 12:
Vn duplex trong Ethernet
Ch full-duplex trong Ethernet Cng ging nh trong Ethernet, ci tin performance ta c th dng ch fullduplex. Fast Ethernet c th cung cp tc truyn ln n 100Mbps trong mi chiu truyn, dn n kt qu 200Mbps throughput. Thng lng ti a 200Mbps ny ch t c khi mt thit b (trm lm vic, server, routers hay mt switch khc) kt ni trc tip n mt switchport. Ni cch khc, cc thit b u cui ca mt kt ni phi h tr fullduplex, c kh nng truyn m khng phi ch pht hin v khi phc khi xung t.
c t ca FastEthernet cng cho php tng thch ngc vi 10Mbps Ethernet truyn thng. Trong trng hp 100BaseTX, cc switchport thng c gi l 10/100 ch ra tc dualspeed. Khi ny, hai thit b hai u kt ni s t ng d tm tc sao cho c hai c th hot ng tc cao nht. Qu trnh d tm ny bao gm vic pht hin v chn la cng ngh lp vt l, tm ch halfduplex hay fullduplex. Nu c hai u ca kt ni c cu hnh theo kiu autonegotiate, tc chung cao nht gia hai thit b s c dng.
Trong qu trnh bt tay d tm ch duplex ca mt kt ni, mt s thng tin s c trao i qua li gia hai thit b. iu ny c ngha l, cho qu trnh d tm t ng l thnh cng, c hai u phi c thit lp ch autonegotiate. Nu khc i (ngha l ch c mt u thit lp autonegotiate), mt u ca kt ni s khng nhn c thng tin t u kia v s khng c kh nng xc nh ch chnh xc ang c dng. Nu qu trnh autonegotiation l tht bi, mt switchport s tr v ch t ng ca n l halfduplex.
Cn ch v vn duplex mismatch khi c hai u ca kt ni u khng cu hnh cho autonegotiation. Khi c mismatch xy ra, mt u ca kt ni s dng full-duplex trong khi u xa dng halfduplex. Kt qu l my trm ang hot ng ch half-duplex s lun pht hin ra collision khi c hai u mun truyn. My trm ang chy full-duplex s gi s l n c quyn truyn bt k thi im no. My trm ny s khng dng li v ch. Tnh trng ny dn n li trn kt ni v tc p ng rt chm gia cc my. Qu trnh bt tay s dng bng cc u tin di y. Khi c hai u kt ni c th bt tay nhau nhiu tc , tc no c u tin cao nht s c dng. V d, nu c hai thit b c th chy mc 6 (100BbaseTX fullduplex) v mc 2 (10base2full), mc 6 s c dng.
u tin 7 6 5 4 3 2 1
Ch ethernet 100Base-t2 (full duplex) 100Base-TX (full duplex) 100BASE-t2 (half duplex) 100Base-T4 100Base-TX 10base-T (full duplex) 10Base-T
m bo cu hnh chnh xc c hai u ca kt ni, Cisco khuyn co cc gi tr v tc truyn, duplex mode phi c cu hnh th cng (manually) trn cc switchports. Yu t ny gip loi tr kh nng mt bn thay i cc ci t, dn n kt ni c th khng dng c. Nu bn cu hnh th cng switchport, hy thit lp lun cho thit b trn u kia ca kt ni cc thng s tng ng. Nu khc i, vn speed mismatch hay duplex mismatch s xy ra.
Bi 13:
Collision domainMin ng v b m chuyn mch: Mt min ng (Collision domain) l mt tp hp cc thit b c th gi cc khung tin m cc khung tin ny c th b ng vi cc khung tin ca mt thit b khc. Trc khi switch c pht minh, Ethernet thng dng hub hoc cc on cp dng chung nh 10Base2 v 10Base5. Switch trong cng ngh Ethernet gip gim kh nng ng thng qua qu trnh lu cc khung tin trong b m v c ch hot ng lp 2 ca n. Theo nh ngha, Hub trong cng ngh Ethernet s bao gm cc c im sau: - Hot ng ch lp 1 ca m hnh tham chiu OSI. - Khuych i, ti to tn hiu in nng chiu di ng truyn.
Min ng (Collision Domain)
Chuyn tn hiu nhn c trn mt cng ra tt c nhng cng khc ngoi tr cng nhn vo, v khng c b m. Nh vy hub s to ra mt min ng . Ngc li, switch s gii hn min ng trn tng cng ca n. Switch cng dng cng loi cp v khuch i tn hiu ging nh hub, nhng switch lm nhiu vic hn. ng s gim thiu do cc khung tin c m, khi switch nhn c cc khung tin trn cc cng khc nhau, switch lu khung tin trong cc b nh m ngn nga xung t. V d, gi s mt switch nhn ba khung tin cng mt thi im i vo ba cng khc nhau v n phi c a ra cng mt cng ca switch. Lc ny switch s lu hai khung tin trong b nh, v chuyn cc khung tin i mt cch tun t. Khi mt cng ca switch kt ni n mt thit b khng phi l HUB, ng s khng th xy ra. Thit b duy nht c th to ra ng l bn thn cng switch v mt thit b kt ni
vo n v nu mi bn c mt cp cp ring truyn. V ng khng th xy ra, nhng phn on mng trn c th s dng ch song cng. ---------------------------------------------------------Bi 14:
Cc phng thc chng loop ca RIPHi t (Convergence) v chng loop: Phn quan trng nht v cng phc tp nht ca RIP nm nhng phng thc chng loop. Ging nh nhng giao thc nh tuyn distance vector khc, RIP s dng kt hp nhng cng c chng loop khc nhau, nhng ng tic rng nhng cng c ny cng lm tng thi gian hi t (convergence) mt cch ng k. S tht, l mt hn ch rt ln ca RIP (k c RIPv2). Bng 8.3 tng hp nhng tnh nng v phng thc lin quan n s hi t v chng loop ca RIP. Tnh nng Split horizon Triggered update M t Thay v qung b tt c cc route ra mt interface, RIP khng qung b nhng route m router hc c t interface ny. Router s gi mt update mi ngay khi thng tin nh tuyn b thay i, thay v phi ch ht thi gian update time. Trigger update cn c tn gi khc l flash update. Khi mt gi tr metric thay i tt hn hoc km hn, router ngay lp tc s gi ra mt thng ip cp nht m khng cn ch cho khong thi gian update timers b ht. Qu trnh ti hi t din ra nhanh hn so vi trng hp phi ch nhng khong thi gian cp nht nh k. Cc thng ip cp nht nh k vn din ra cng vi cc thng ip trigger update. Nh vy mt router c th nhn mt thng tin km v mt route t mt router cha hi t sau khi nhn mt thng tin chnh xc t mt trigger update. Tnh hung ny xy ra v cc li nh tuyn vn c th xy ra trong qu trnh ti hi t. Mt s hiu chnh xa hn na l trong thng ip cp nht, ch bao gm cc a ch mng lm cho vic trigger xy ra. K thut ny lm gim thi gian x l v gim nh hng n bng thng. khi route b li, router s gi update v route i vi infinity-metric (hop count = 16). Router nhn c qung b v mt poisoned route (metric 16) trn mt interface, router s hi p li thng ip
Route poisoning Poison reverse
Update timer
Holddown timer
poison reverse trn cng interface . Qua mi khong thi gian update timer, router s gi update mt ln qua mt interface, mi interface c mt update timer ring, mc nh trn tt c interface l 30 giy. i vi mi route n mt subnet trong bng nh tuyn, nu nh metric ca route thay i n mt gi tr ln hn, thi gian holddown timer s bt u. Trong khong thi gian ny (mc nh l 180 giy) router s khng cp nht route no khc n subnet trong bng nh tuyn cho n khi thi gian holddown timer kt thc. Trigger update s lm tng kh nng p ng mt h thng mng ang hi t. Holddown timers s gip kim sot cc thng tin nh tuyn xu. Nu khong cch n mt mng ch tng (v d s hop count tng t hai ln bn), router s gn mt gi tr thi gian cho route . Cho n khi no thi gian ht hn, router s khng chp nhn bt k cp nht no cho route . R rng c mt s nh i y. Kh nng cc thng tin nh tuyn km b a vo bng nh tuyn l gim nhng b li thi gian hi t s tng ln. Nu thi gian holdown l qu ngn, n s khng hiu qu. Nu khong thi gian l qu di, qu trnh nh tuyn thng thng s b nh hng. i vi mi route tn ti trong bng nh tuyn, thi gian invalid timer s tng cho n khi router nhn c update thng bo v route . Nu nh nhn c update, thi gian invalid s c t v 0. Nu nh router khng nhn c update, m thi gian invalid ht (mc nh l 180 giy), route c xem nh l khng dng c. Thi gian flush timer mc nh l 240 giy, cng ging nh thi gian invalid timer, tuy nhin thi gian flush timer mc nh s tng thm 60 na, trong thi gian ny nu khng nhn c update v route, router s loi route ra khi bng nh tuyn.
Invalid timer
Flush (Garbage) timer
Bi 15:
Tt Frame Relay InARPTt InARP: Trong hu ht nhng m hnh mng c a ra, vic s dng InARP l hp l. Tuy nhin, ta c th tt InARP trn interface vt l hay multipoint interface i bng cch s dng lnh no frame-relay inverse-arp trn interface subcommand. C th ngng hot ng InARP trn tt c cc VC ca interface/subinterface, tt c cc VC ca interface/subinterface ng vi mt giao thc L3 ring bit, hay n thun l trn mi DLCI c th. Cu lnh no frame-relay inverse-arp khng ch lm cho router ngng vic gi thng ip InARP ra ngoi, m cn lm cho router khng nhn thng ip InARP. Ly v d, cu lnh no frame-relay inverse-arp ip 400 mode subinterface trn Router R1 trong v d 1.2 khng ch ngn R1 ngng gi thng ip InARP ra DLCI400 ti R4 m cn lm cho R1 b i thng ip InARP nhn trn DLCI400. Bng 15.1 : Tng hp mt s c tnh chi tit v Frame Relay Inverse ARP trn IOS Interface Point-toCch c x trn mi kiu point interface ring bt InARP c i hi LMI khng Lun lun ? InARP c kch hot mt ng cch mc nh ? C th tt hot ng ca C InARP khng ? C th b qua thng ip Lun lun (*) InARP nhn hay khng Interface multipoint hoc interface vt l Lun lun ng Khng Khi InARP b tt i
(*) Interface point-to-point lun lun b qua thng ip InARP, bi v i vi point-to-point interface, ch dng mt DLCI gi n tt c a ch trong cng mt subnet. -------------------------------------------------------
Bi 16:
Giao thc Frame Relay InverseARPFrame Relay Inverse ARP: IP ARP c bit n nh mt giao thc ph thng v tng i n gin. i vi k thi CCIE cng vy. a s cc cu hi trong phn IP ARP l nhng cu hi n gin. Do , nhng cu hi kh v ch xy dng CEF adjacency table s tp trung vo Frame Relay Inverse ARP, cng chnh v vy m phng thc Frame Relay Inverse ARP s c trnh by c th v chi tit hn. Tng t nh IP ARP, nhim v ca InARP l phn gii gia a ch L3 v a ch L2. a ch L3 chnh l a ch IP, cn a ch L2 y chnh l s DLCI (tng t nh a ch MAC trong IP ARP). Tuy nhin, trong phng thc InARP, router bit c a ch L2 (DLCI), v cn phn gii ra a ch L3 (IP) tng ng.
Hnh sau l mt v d v chc nng ca InARP.
Trong mi trng LAN, i hi phi c mt gi tin (ARP request) n host v kch hot giao thc IP ARP trn host (tr v ARP reply). Tuy nhin , trong mi trng WAN, khng cn mt gi tin no n router kch hot InARP trn router ny, thay vo l mt thng ip v tnh trng LMI (Local Management Interface) s c dng.
Sau khi nhn c thng ip trng thi LMI l LMI PVC Up, router s loan bo a ch IP ca n ra mch lin kt o (VC Virtual Circuit) tng ng thng qua thng ip InARP (nh ngha trong RFC1293). Nh vy, mt khi LMI khng c thc thi th InARP cng khng hot ng bi v khng c thng ip no ni cho router bit gi thng ip InARP. Trong mng Frame Relay, nhng cu hnh chi tit c chon la vi mc ch trnh mt s tnh trng khng mong mun, nhng tnh trng ny s c m t chi tit trong nhng trang k tip ca chng ny. V d khi s dng point-topoint subinterface, vi mi VC thuc mt subnet ring, tt c nhng vn gp phi trong cu hnh ny s c m t r rng c th phng trnh. Bn thn giao thc InARP tng i n gin. Tuy nhin, khi trin khai InARP trn nhng m hnh mng khc nhau, da trn nhng kiu cng khc nhau (cng vt l, cng point-to-point subinterface v multipoint subinterface) th cch thc hot ng ca InARP s tr nn phc tp hn rt nhiu. Sau y l mt v d v h thng mng Frame Relay c thit k theo m hnh mng li khng y (partial mesh) trn cng mt subnet trong khi mi router s dng mt kiu cng khc nhau.
S mng trn ch mang tnh cht l mt v d, n ch s dng trong mi trng hc tp hiu chi tit hn v cch thc hot ng ca InARP. S ny khng nn c p dng trong mi trng mng thc t bi thit k yu km vi nhiu hn ch khi trin khai giao thc nh tuyn bn trn. u tin cu hnh frame relay trn cng multipoint ca R1.
Router1# sh run ! Lines omitted for brevity interface Serial0/0 encapsulation frame-relay interface Serial0/0.11 multipoint ip address 172.31.134.1 255.255.255.0 frame-relay interface-dlci 300 frame-relay interface-dlci 400 ! Lines omitted for brevity K tip, cng serial c tt v bt v cc hng trong InARP trc b xa v vy ta c th quan st tin trnh InARP. Router1# conf t Enter configuration commands, one per line. End with CNTL/Z. Router1(config)# int s 0/0 Router1(config-if)# do clear frame-relay inarp Router1(config-if)# shut Router1(config-if)# no shut Router1(config-if)# ^Z Cc thng ip t lnh debug frame-relay event hin th cc thng ip nhn c InARP trn R1. Ch cc gi tr hex 0xAC1F8603 v 0xAC1F8604, vi cc gi tr thp phn tng ng l 172.31.134.3 and 172.31.134.4 (tng ng vi Router3 v Router4).
Router1# debug frame-relay events *Mar 1 00:09:45.334: Serial0/0.11: FR ARP input *Mar 1 00:09:45.334: datagramstart = 0392BA0E, datagramsize = 34 *Mar 1 00:09:45.334: FR encap = 048C10300 *Mar 1 00:09:45.334: 80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00 *Mar 1 00:09:45.334: AC 1F 86 03 48 C1 AC 1F 86 01 01 02 00 00 *Mar 1 00:09:45.334: *Mar 1 00:09:45.334: Serial0/0.11: FR ARP input *Mar 1 00:09:45.334: datagramstart = 0392B8CE, datagramsize = 34 *Mar 1 00:09:45.338: FR encap = 064010300 *Mar 1 00:09:45.338: 80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00 *Mar 1 00:09:45.338: AC 1F 86 04 64 01 AC 1F 86 01 01 02 00 00 K tip, ch lnh show frame-relay map c bao gm t kha dynamic, ngha l cc hng c hc thng qua InARP. Router1# show frame-relay map Serial0/0.11 (up): ip 172.31.134.3 dlci 300(012C,048C0), dynamic, broadcast, status defined, active Serial0/0.11 (up): ip 172.31.134.4 dlci 400(0190,06400), dynamic, broadcast, status defined, active Trn R3, lnh show frame-relay map ch lit k mt hng duy nht nhng nh dng th khc. Bi v R3 dng point-to-point subinterface, hng ny khng c hc thng qua InARP v kt qu lnh khng bao gm t kha Dynamic. Cng ch l kt qu khng cho thy a ch Layer 3 no.
Router3# show frame-relay map Serial0/0.3333 (up): point-to-point dlci, dlci 100(064,01840), broadcast status defined, active Ch : Trong v d trn ta thy xut hin lnh do trong ch cu hnh. Lnh do cho php cu hnh trong configuration mode nhng thc hin chc nng exec mode m khng phi thot khi mode configuration. V d lnh do clear frame-relay inarp thc hin configuration mode tng ng vi vic ta thc hin lnh clear frame-relay inarp ch ton cc. Trong v d trn, lnh show cho thy Router R1 nhn v s dng thng tin InARP; tuy nhin Router R3 th khng s dng thng tin InARP nhn vo. H iu hnh Cisco IOS hiu rng ch mt VC c thit lp vi mt subinterface point-to-point; mi mt a ch IP u cui khc trn cng mt subnet ch c th tham chiu n duy nht mt s DLCI. V vy, mi thng tin InARP nhn c lin kt n s DLCI l khng cn thit. Ly v d, khi no Router R3 cn gi mt gi tin n Router R1(172.31.134.1), hay n mi u cui khc trong subnet 172.31.134.0/24. T chnh cu hnh ca mnh, Router R3 bit rng phi gi qua s DLCI trn point-to-point subinterface , ngha l qua DLCI 100. V vy, mc d c ba kiu cng c dng cho cu hnh Frame Relay h tr InARP mt cch mc nh, point-topoint subinterface s b qua thng tin InARP nhn c. ---------------------------------------------------Bi 17: Gii thiu v IPv6 Hai vn ln m IP v.4 ang phi i mt l vic thiu ht cc a ch, c bit l cc khng gian a ch tm trung (lp B) v vic pht trin v kch thc rt nguy him ca cc bng nh tuyn trong Internet. Trong nhng nm 1990, CIDR c xy dng da trn khi nim mt n a ch (address mask). CIDR tm thi khc phc c nhng vn nu trn. Kha cnh t chc mang tnh th bc ca CIDR ci tin kh nng m rng ca IPv.4. Mc d c thm nhiu cng c khc ra i nh k thut subnetting (1985), k thut VLSM (1987) v CIDR (1993), cc k thut trn khng cu vt IP v.4 ra khi mt vn n gin: khng c a ch cho cc nhu cu tng lai. C khong 4 t a ch IPv.4 nhng khong a ch ny l s khng trong tng lai vi nhng thit b kt ni vo Internet v cc thit b ng dng trong gia nh c th yu cu a ch IP.
Mt vi gii php tm thi, chng hn nh dng RFC1918 trong dng mt phn khng gian a ch lm cc a ch dnh ring v NAT l mt cng c cho php hng ngn hosts truy cp vo Internet ch vi mt vi IP hp l. Tuy nhin gii php mang tnh di hn l vic a vo IPv.6 vi cu trc a ch 128-bit. Khng gian a ch rng ln ca IPv.6 khng ch cung cp nhiu khng gian a ch hn IPv.4 m cn c nhng ci tin v cu trc. Vi 128 bits, s c 340,282,366,920,938,463,463,374,607,431,768,211,456 a ch. Trong nm 1994, IETF xut IPv.6 trong RFC 1752. IPv.6 khc phc vo mt s vn nh thiu ht a ch, cht lng dch v, t ng cu hnh a ch, vn xc thc v bo mt. i vi mt doanh nghip dng h tng mng theo IPV4, chuyn sang IPv6 khng phi l vic d dng. Mt giao thc IP mi s yu cu cc phn mm mi, cc phn cng mi v cc phng php qun tr mi. Cng c th, IPv4 v IPv6 s cng tn ti, ngay c bn trong mt Autonomous System trong khong thi gian sp ti. IP v.6 c cc c im v li ch nh sau: Khng gian a ch rng ln a ch unicast v a ch multicast Tng hp a ch (address aggregation) T ng cu hnh Renumbering Cu trc header n gin, hiu qu Bo mt C ng Cc tu chn chuyn i t IPv4 sang IPv6 Nh c nh ngha trong RFC1884 v RFC2373, cc a ch IPv6 l 128-bit dng nhn dng cho cc cng ca routers v tp cc cng ca routers. C ba kiu a ch tn ti: - Unicast: l a ch cho mt giao tip. Mt gi d liu c gi ti mt a ch Unicast s c phn phi ti cng giao tip c ch ra bi a ch . - Anycast: l a ch cho tp hp cc cng giao tip. Cc tp ny thng thng thuc v cc node khc nhau. Mt gi d liu c gi ti mt a ch anycast s c phn phi n cng giao tip gn nht hay u tin trong nhm anycast.
- Multicast: a ch cho mt tp hp cc cng giao tip (thng thng thuc v cc node khc nhau). Khi mt gi c gi n mt a ch multicast, tt c cc cng giao tip s nhn c gi d liu ny. vit mt a ch dng 128-bit dng d c hn, kin trc ca IPv6 loi b dng c php du chm thp phn ca IPv4 m ch dng dng thp lc phn. V vy, IPv6 c th c vit bao gm 32 k t dng hex vi du hai chm : tch a ch ra thnh tm phn, mi phn c chiu di 16-bit. Theo cc k hoch hin ti, cc node chy IPv6 kt ni vo Internet s dng mt k thut gi l a ch kh kt ton cc (aggregatable global unicast address). Trong c nhiu im tng ng vi k thut summary nh trong version 4. a ch tch hp ca IPv6 c ba mc: Mc public topology: l tp hp cc nh cung cp kt ni Internet. Mc vng: mc ny l cc b i vi cc t chc. Mc cng giao tip: mc ny nh hng n cc cng giao tip ring l. Linklocal address l a ch ch c s dng trn 1 kt ni (hay 1 cng ca router) v a ch ny phi duy nht trong lin kt . a ch ny c th c s dng trong mng cc b (cc my c chung a ch mng )v c th khng c router trong mng ny. a ch ny c dng :FE80::. Subnet ID ca lai a ch ny c gn =0. Do lai a ch ny khng th c s dng giao tip ra khi subnet cc b c. ----------------------------------------------------Bi 18:
Khi nim Vlan (CCNA level)Trong mi trng Ethernet LAN, tp hp cc thit b cng nhn mt gi broadcast bi bt k mt thit b cn li c gi l mt broadcast domain. Trn cc switch khng h tr VLAN, switch s y tt c cc broadcast ra tt c cc cng, ngoi tr cng m n nhn frame. Kt qu l, tt c cc interface trn loi switch ny l cng broadcast domain. Nu switch ny kt ni n cc switch v cc hub khc, cc cng trn switch ny cng s trong cng broadcast domain. Mt VLAN n gin l mt tp hp ca cc switchport nm trong cng broadcast domain. Cc cng c th c nhm vo cc vlan khc nhau trn tng switch v trn nhiu switch. Bng cch to ra nhiu VLAN, cc switch s to ra nhiu broadcast domains. Khi , khi c mt broadcast c gi bi mt thit b nm trong mt vlan s c chuyn n nhng thit b khc trong cng
vlan, tuy nhin broadcast s khng c forward n cc thit b trong vlan khc. Mi Vlan nn c mt ip subnet hay ni cch khc, cc thit b trong mt vlan thng dng chung mt dy a ch IP.Tuy nhin, ta vn c th t nhiu a ch trong mt vlan v dng secondary address trn cc routers nh tuyn gia cc vlan v cc subnets. Bn cng c th thit k mt mng dng ch mt subnets trn nhiu vlan v dng routers vi chc nng proxy-arp chuyn traffic gia cc hosts trong cc vlan ny. Private vlan c th c xem nh gm mt subnet trn nhiu vlan. Cc L2 switch chuyn cc frame gia cc thit b trn cng mt vlan nhng n khng chuyn frame gia cc thit b khc vlan. chuyn d liu gia hai vlan, mt thit b L3 switch hoc routers phi c dng. VLAN Trunking Protocol: VTP qung b cc thng tin cu hnh vlan n cc switch lng ging cc cu hnh vlan c th c thc hin trn mt switch, trong khi tt c cc switch khc trong h thng mng s hc thng tin vlan. VTP thng qung b cc thng tin nh vlan ID, vlan name v kiu vlan cho tng vlan. Tuy nhin, VTP thng khng qung b bt c thng tin no v cc switchport no trong tng vlan no, v vy cu hnh kt hp switch interface no vi vlan no vn phi c cu hnh trn tng switch. Ngoi ra, s tn ti ca vlan ID c dng cho private vlan cng c qung b, nhng cc thng tin chi tit bn trong private vlan cng s khng c qung b bi VTP.
Chc nng Gi ra cc thng tin qung b VTP X l cc thng tin VTP nhn c cp nht cu hnh vlan Trung chuyn cc thng tin qung b ca VTP Lu thng tin vlan trong NVRAM hay vlan.dat C th to, thay i v xa vlan dng cc lnh cu hnh
Server mode Yes Yes Yes Yes Yes
Client No Yes Yes No No
Transparent No No Yes Yes Yes
Cc tin trnh VTP v ch s revision number: Tin trnh cp nht ca VTP
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