Module 2 Configuring EIGRP Lesson 1 Introducing EIGRP EIGRP capabilities and attributes: (Cisco proprietary protocol) Fast convergence Loop free DUAL (Diffusing Update Algorithm) VLSM & discontinuous subnetworks support Partial updates – triggered updates Multiple network-layer protocol support – IP, AppleTalk, Novel NetWare IPX Seamless connectivity across all data link layer protocols and topologies Sophisticated metric – 32 bit Multicast & unicast – 224.0.0.10 EIGRP Key Technologies: Neighbor discovery/recovery - hello Reliable transport protocol (RTP) DUAL finite-state machine Protocol-dependent modules (PDMs) Neighbor Table: List adjacent routers ( topology table –learned routes to each destination, feasible successor route routing table – best route to each destination, successor route best route – successor route feasible successor route – backup route to a destination, in topology table) Neighbor’s adderss & interface Neighbor -> hello (hold time) -> no response -> DUAL is informed of the topology change DUAL Select loest-cost, loop-free paths AD (Advertised Distance) = cost <next-hop router - destination> FD (Feasbible Distance) = cost <local - destination> = AD + cost <local – netx-hop router> Lowest-cost = lowest FD (Current) successor – next-hop router with lowest-cost, loop-free path – lowest FD Feasible successor – backup router with loop-free path (AD of feasible successor < FD of current successor route) Default 4 successors can be added to the routing table. Max 6 Topology Table: Contain all destinations advertised by neighboring routiers Maintains the metric that each neighbor advettises for each destination (AD) & the metric that this router would use to reach the destination via that neighbor (FD)
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Module 2 Configuring EIGRPblljw/PDF/EIGRP.pdfPoint-to-point subinterfaces using Frame Relay: - T1 by default - manually configure bandwidth to match the contracted committed information
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Module 2 Configuring EIGRP
Lesson 1 Introducing EIGRP
EIGRP capabilities and attributes: (Cisco proprietary protocol) � Fast convergence � Loop free � DUAL (Diffusing Update Algorithm) � VLSM & discontinuous subnetworks support � Partial updates – triggered updates � Multiple network-layer protocol support – IP, AppleTalk, Novel NetWare IPX � Seamless connectivity across all data link layer protocols and topologies � Sophisticated metric – 32 bit � Multicast & unicast – 224.0.0.10 EIGRP Key Technologies: � Neighbor discovery/recovery - hello � Reliable transport protocol (RTP) � DUAL finite-state machine � Protocol-dependent modules (PDMs) Neighbor Table: � List adjacent routers ( topology table –learned routes to each destination, feasible successor route routing table – best route to each destination, successor route best route – successor route feasible successor route – backup route to a destination, in topology table) � Neighbor’s adderss & interface � Neighbor -> hello (hold time) -> no response -> DUAL is informed of the
netx-hop router> � Lowest-cost = lowest FD � (Current) successor – next-hop router with lowest-cost, loop-free path – lowest
FD � Feasible successor – backup router with loop-free path
(AD of feasible successor < FD of current successor route) � Default 4 successors can be added to the routing table. Max 6 Topology Table: � Contain all destinations advertised by neighboring routiers � Maintains the metric that each neighbor advettises for each destination (AD) &
the metric that this router would use to reach the destination via that neighbor (FD)
� Changed when a directly connected route or interface changes or when a neighobring router reports a change to a route
� Two states: active / passive � Active: the router is performing a recomputation � Passive: the router is not performing a recomputation (desired state) Routing Table: � The lowest FD – successor router EIGRP Packets: � Hello: neighbor discovery – multicasts, no acknowledgement requirement � Update: unicast to specific router or multicast to multiple router � Query: ask for feasible successor – multicast but can be retransmitted as unicast � Reply: unicast � ACK: for update, query and reply – unicast hello packets and contain a nonzero
acknowledge number
EIGRP Metric: (bandwidth & delay by default. 256 * IGRP metric) � Bandwidth: smallest bandwidth between source and destination � Delay: cumulative interface delay along the path � Reliability: worst reliability between source and destination, based on keepalives � Loading: worst load on a link between source and destination � MTU: (Maximum Transmission Unit) smallest MTU in the path EIGRP Metric Calculation: � Default : K1=K3=1, K2=K4=K5=0 � Default: Metric = bandwidth (slowest link)+ delay (sum of delay) � Metric = (K1*bandwidth) + [(K2*bandwidth)/(256-load)] + (K3*delay) � If K5 not equal to 0 Metric = Metric * [K5/(reliability + K4)] � Delay: sume of delay in the path, in 10ms, multiplied by 256 � Bandwidth = [10^7 / (minimum bandwidth link along the path, in kbps)] * 256 � K values are carried in EIGRP hello packets. Integrating the EIGRP & IGRP Routes � EIGRP: 32 bit; IGRP: 24 bit � EIGRP metric = IGRP metric * 256
IP-EIGRP Topology Table for AS(100)/ID(192.168.1.101)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 192.168.1.96/27, 1 successors, FD is 40512000
via Connected, Serial0/0/1
P 192.168.1.0/24, 1 successors, FD is 40512000
via Summary (40512000/0), Null0
P 172.16.0.0/16, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 172.16.1.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 172.17.0.0/16, 1 successors, FD is 40514560
via 192.168.1.102 (40514560/28160), Serial0/0/1
R1#show ip eigrp traffic
IP-EIGRP Traffic Statistics for AS 100
Hellos sent/received: 429/192
Updates sent/received: 4/4
Queries sent/received: 1/0
Replies sent/received: 0/1
Acks sent/received: 4/3
Input queue high water mark 1, 0 drops
SIA-Queries sent/received: 0/0
SIA-Replies sent/received: 0/0
Hello Process ID: 113
PDM Process ID: 73
Lesson 3 Confirguring Advanced EIGRP Options
Automatic summarization: default - enable Manual summarization: � When the last specific route of summary goes away, the summary is deleted � Metric: minimum � Summary routes to interface null0 � R(config-router)#no auto-summary � R(config-if)#ip summary-address eigrp as-number address
mask [admin-distance]
Load Balancing Across Equal Paths: � Default – 4; Max – 6 (command: maximum-paths maximum-path) � maximum-path = 1 – disable load balancing � fast-switched – on a per-packet basis Load Balancing Across Unequal-Cost Paths: � R(config-router)#variance multiplie
� Two feasiblity conditions: 1. the loacl best metric (the current FD) > the best metric (AD) learned from the next router. 2. multiplie * the current FD > the metric throught the next route (alternative FD)
EIGRP Bandwidth Use Across WAN Links � Support : point-to-point links
ip bandwidth-percent eigrp as-number percent (percent can be greater than 100) Bandwidth Utilization over WAN Interfaces � Point-to-point subinterfaces using Frame Relay:
- T1 by default - manually configure bandwidth to match the contracted committed information rate (CIR) of the permanent virtual circuit (PVC). � Multipoint Frame Relay, ATM, ISDN PRI:
- all neighbors share the bandwidth equally - EIGRP uses the bandwidth on the physical interface divided by the number of neighbors on that interface to calculate the bandwidth attributed per neighbor � Each PVC can have a different CIR, creating an EIGRP packet-pacing problem � Multipoint intervace – convert these to point-to-point configuration or manually
configure bandwidth by multiplying the lowest CIR by the number of PVCs EIGRP WAN Configuration: � Frame Relay Hub-and-Spoke Topology
- configure each virtual Circuit as point-to-point, specify bandwidth = 1/10 of link capacity - increase EIGRP utilization to 50% of actual VC capacity
Route Authentication � Simple password (plain-text): IS-IS, OSPF, RIPv2 � MD5: OSPF, RIPv2, BGP, EIGRP EIGRP MD5 Authentication � Router generates and checks every packet. Router authenticates the source of
each routing update packet that it receives. � Configure a key (password) and key ID on both the sending and the receiving
router; each participating neighbor must have same key configured. � Rotuer generates a message digest, or hash, of the key, key ID, and message � EIGRP allows keys to be managed using key chains � Specify key ID (number), key, and lifetime of key. (key activation times overlap
to avoid any period of time for which no key is activated.) � Fisrt valid actived key, in order of key numbers, is used Configuring MD5 Authentication � R(config-if)#ip authentication mode eigrp
send-lifetime 04:00:00 Jan 1 2006 04:01:00 Jan 1 2006
key 2
key-string secondkey
accept-lifetime 04:00:00 Jan 1 2006 infinite
send-lifetime 04:00:00 Jan 1 2006 infinite
<output omitted>
interface FastEthernet0/0
ip address 172.16.1.1 255.255.255.0
!
interface Serial0/0/1
bandwidth 64
ip address 192.168.1.101 255.255.255.224
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 R1chain
!
router eigrp 100
network 172.16.1.0 0.0.0.255
network 192.168.1.0
auto-summary
<output omitted>
key chain R2chain
key 1
key-string firstkey
accept-lifetime 04:00:00 Jan 1 2006 infinite
send-lifetime 04:00:00 Jan 1 2006 infinite
key 2
key-string secondkey
accept-lifetime 04:00:00 Jan 1 2006 infinite
send-lifetime 04:00:00 Jan 1 2006 infinite
<output omitted>
interface FastEthernet0/0
ip address 172.17.2.2 255.255.255.0
!
interface Serial0/0/1
bandwidth 64
ip address 192.168.1.102 255.255.255.224
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 R2chain
!
router eigrp 100
network 172.17.2.0 0.0.0.255
network 192.168.1.0
auto-summary
Lesson 5 Using EIGRP in an Enterprise Network
Factors that Influence EIGRP Scalability � Quantity of routing information exchanged between neighbors; without proper
route summarization, this can be excessive � Number of routers that must be invlved when a topoloy change occurs � Depth of topology: the number of hops that information must travel to reach all
routers � Number of alternate paths rhrouth the network. (stuck in active (SIA)) EIGRP Query Process � Queries are sent when a route is lost and no feasible successor is available � The lost route is now in active state � Queries are sent to all neighboring routers on all interfaces except the interface to
the successor � If the neighbors do not have the lost-route information, queries aer sent to their
neighbors � If a router has an alternate route, it answers the qurey; this stops the query form
speading in that branch of the network EIGRP Stub � The EIGRP stub routing feature improves network stability, reduces resource
utilization, and simplifies remote router (spoke) configuration. � Stub routing is commonly used in a hub-and-spoke topology. � A stub router sends a special peer information packet to all neighboring routers to
report its status as a stub router. � A neighbor that receives a packet informing it of the stub status does not query
the stub router for any routes. Configuring EIGRP Stub � R(config-router)#eigrp stub [receive-only | connected |
static | summary] - receive-only: Prevent the stub from sending any type of route. - connected: Permits stub to send connected routes (may still need to redistribute) (command: redistribute connected). - static: Permits stub to send static routes (must still redistribute) (command: redistribute static). - summary: Permits stub to send summary routes. (command: ip summary-address or auto-summary) - Default - connected and summary
Limiting Updates and Queries: Using EIGRP Stub � R(config)#router eigrp 1 � R(config-router)#eigrp stub Example: eigrp stub Parameters � If stub connected is configured:
- B will advertise 10.1.2.0/24 to A. - B will not advertise 10.1.2.0/23, 10.1.3.0/23, or 10.1.4.0/24.
� If stub summary is configured: - B will advertise 10.1.2.0/23 to A. - B will not advertise 10.1.2.0/24, 10.1.3.0/24, or 10.1.4.0/24.
� If stub static is configured:
- B will advertise 10.1.4.0/24 to A. - B will not advertise 10.1.2.0/24, 10.1.2.0/23, or 10.1.3.0/24. � If stub receive-only is configured:
- B will not advertise anything to A, so A needs to have a static route to the networks behind B to reach them.
SIA Connections: (Stuck in Active) � The router has to get all replies form the neighbors with an outstanding query
before the router calculates the successor information � If any neighbor fails to reply to the query within 3 minutes by default, the route is
SIA, and the router resets the neighbor relationship with the neighbor that fails to reply.
Most Common Reasons for SIA Routes: � The router is too busy to answer the query – high CPU, membory problems � The link between the two routers is not good – some packets are lost � A failure causes traffic on a link to flow in only one direction – unidirectional link Preventing SIA Connections: Graceful Shutdown � Goodbye message is broadcast when an EIGRP ruting process is shut down, to
inform adjacent peers about the impending topology change.
� Before Router A resets relationship to router B when the normal active timer expires. However, the problem is the link between router B and C.
� After Router A sends an SIA-Query at half of the normal active timer. Router B acknowledges the query there by keeping the relationship up.