Ospf

OSPF (Open Shortest Path First)

Alp IIK

Netas NTS Engineer

[email_address]

3. Open Shortest Path First (OSPF) Section 1 OSPF Overview 4.

Overview

In an OSPF network, each router maintains alink state databasethat

describes the topology of the autonomous system (AS). The database

contains thelocal statefor each router in the AS, including the routers

usable interfaces and reachable neighbors. Each router periodically checks

for changes in its local state and shares any changes detected by flooding

link state advertisements(LSA) throughout the AS. Routers synchronize

their topological databases based on the sharing of information from LSAs.

From the topological database, each router constructs ashortest-path tree ,

with itself as the root. The shortest-path tree gives the optimal route to each

destination in the AS. Routing information from outside the AS appears

on the tree as leaves.

OSPF routes IP traffic based solely on the destination IP address and

subnet mask, and IP TOS contained in the IP packet header.

Autonomous system

The autonomous system (AS) can be subdivided into areas that group

together contiguous networks, routers connected to these networks, and

attached hosts. Each area has its own topological database, which is

invisible from outside the area. Routers within an area know nothing of the

detailed topology of other areas. Subdividing the AS into areas significantly

reduces the amount of routing protocol traffic as compared to treating the

entire AS as a single link state domain.

6. Feature Updates Update type Transport Authentication Metric Metric type Topology size Convergence RIPv2 Periodic Broadcast/Multicast UDP Simple and MD5 Hops Distance vector IS-IS Incremental L2 Multicast Layer 2 Simple and MD5 Cost Link-state OSPF Incremental L3 Multicast IP Simple and MD5 Cost Link-state Small/Medium Slow Fast Large Fast Large 7. OSPF Path Determination

OSPF uses SPF for path determination.

SPF uses cost values to determine the best path to a destination.

RTR-A RTR-C RTR-B Cost 0 Cost 10 Cost 125 Cost 125 Cost 135 RTR-A 10.0.0.0 Cost 260 via RTR C *10.0.0.0 Cost 135 via RTR B * = Best path 10.0.0.0 8. Calculating Link Cost

Cost = reference-bandwidth bandwidth

The default reference-bandwidth is 100 000 000 kb/s or100 Gb/s.

The default auto-cost metrics for various link speeds are as follows:

10-Mb/s link default cost of 10 000

100-Mb/s link default cost of 1000

1-Gb/s link default cost of 100

10-Gb/s link default cost of 10

The cost is configurable.

9. Configuration Basics

Interfaces must be configured in an OSPF area.

Verify that adjacencies are formed with neighbors.

Verify that routes are in the routing table.

10. Open Shortest Path First (OSPF) Section 2 OSPF Packet Types 11. Section Objectives

This section describes the operation of OSPF:

OSPF packet types

Communication with other routers

Forming adjacencies

Election and purpose of the designated router

Topology changes

12. OSPF Multicast Addressing

Specially reserved addresses for OSPF:

224.0.0.5: All routers that speak OSPF on the segment

224.0.0.6: All DR/BDRs on the segment

IP multicast addresses use the lower 23 bits of the IP address as the low-order bits of the MAC multicast address 01-005E-XX-XX-XX.

224.0.0.5 = MAC 01-00-5E-00-00-05

224.0.0.6 = MAC 01-00-5E-00-00-06

13. OSPF Generic Packet

OSPF packets use protocol number 89 in the IP header.

OSPF is its own transport layer.

Alcatel-Lucent Interior Routing Protocols and High Availability IP header protocol ID 89 = OSPF Link header IP header OSPF packet types Link trailer 14. OSPF Packet Header

The OSPF packet is divided into the following fields.

Each field is always present in any OSPF packet sent.

Versionnumber Type Packetlength Router ID Area ID Check- sum Authen-ticationtype Authen-tication Data 15. OPSF Packet Types

OSPF hello

OSPF database descriptor

OSPF link-state request

OSPF link-state update

OSPF link-state ACK

Alcatel-Lucent Interior Routing Protocols and High Availability 16. OSPF Authentication

OSPF supports three types of authentication:

No authentication (default)

Simple authentication

MD5 authentication

17. OSPF Hello Packet Overview Hello * These aspects of the hello packet must match for all neighbor routers on the segment.

The hello packet aids in establishing adjacencies.

Hello packet information Router IDArea ID* Authentication and Password* Hello and dead intervals * Stub area flag* Priority value DR IP address BDR IP address Neighbors 18. OSPF Hello Packet Format Checksum Router ID Area ID AuType Version# 1 Packet length Authentication Authentication Network mask Hello interval Options Rtr Pri Router dead interval Designated router Backup designated router Neighbor 0 31 19. OSPF Adjacencies

Establishing an adjacency:

1.1.1.1 1.1.1.2 (1) (2) (3)

Hello, RID=1.1.1.1

No neighbors known

(2)Hello, RID= 1.1.1.2 I see neighbor 1.1.1.1 2-Way Hello (4)Hello, RID=1.1.1.1 I see neighbor 1.1.1.2 20. OSPF Database Descriptor Packet Format Checksum Router ID Area ID AuType Version# 2 Packet length Authentication Authentication Interface MTU Options DD sequence number LSA header 0 0 0 0 0 M MS 0 31 21. OSPF Adjacencies (continued)

1.1.1.1 1.1.1.2 1/1 1/1 (1) (2) (3) (4) (1)DBD: RID = 1.1.1.1(2)DBD: RID = 1.1.1.2 Exchange Exstart (3)DBD: Summary of all networks known (4)DBD: Summary of all networks known (Higher RID begins) 22. OSPF Link-State Request Packet Format Checksum Router ID Area ID AuType Version# 3 Packet length Authentication Authentication LS type Advertising router Link-state ID 0 31 23. OSPF Link-State Update Packet Format Checksum Router ID Area ID AuType Version# 4 Packet length Authentication Authentication No. of Advertisements List of LSAs 0 31 24. OSPF LSR and LSU Exchange

1.1.1.1 1.1.1.2 E0 E0 (1) (2) (3) (4) (1)LSR: Send information for the Following networks (2)LSR: Send information for thefollowing networks(3)LSU: Here is what you requested (4)LSU: Here is what you requested 25. OSPF Completing the Exchange of Information

1.1.1.1 1.1.1.2 E0 E0 (1) (2) (3) (4) (1)ACK: Thanks for the information (2)ACK: Thanks for the information (3)Hello (4)Hello Full adjacency 26.

On point-to-point links, there is no need for a DR or BDR.

All packets are sent via IP multicast address 224.0.0.5.

Usually a leased-line (i.e., HDLC, PPP) segment

Can be configured on point-to-point Ethernets

OSPF Point-to-Point Segments RTR - A RTR - C RTR - B Network 2.2.2.0/24 27. OSPF LAN Communication

Election of the DR and BDR in multi-access networks:

C 1.1.1.1 D 1.1.1.2 E 1.1.1.3 A 1.1.1.5 B 1.1.1.4

Each router sends hellos.

The router with the highest priority is the DR.

If all priorities are the same, the DR is the router with the highest RID.

RTR-A Has the highest RID, so it will be the DR RTR-B Has the second highest RID, so it will be the BDR 28. OSPF Exchanging Updates in a LAN

Election of the DR and BDR in multi-access networks:

RTR-C 1.1.1.1 D 1.1.1.2 E 1.1.1.3 RTR-A (DR) 1.1.1.5 RTR-B (BDR) 1.1.1.4

Routers use the 224.0.0.6 IP address to send updates to the DRs.

The BDR monitors the DR to ensure that it sends updates.

The DR uses 224.0.0.5 to send updates to all OSPF routers.

RTR-C sends update to All DRs using IP address 224.0.0.6 RTR-A sends update to All OSPF routers usingIP address 224.0.0.5 29. OSPF Adding a Router to a LAN DR BDR New router *The new router uses IP address 224.0.0.5 to send a hello. All routers will see the hello. Hello, RID = 1.1.1.3 I see no others RID 1.1.1.3 RID 1.1.1.1 RID 1.1.1.2 30. OSPF Learning Which Is the DR/BDR in a LAN DR BDR New router *The new router waits to see if any other router speaks OSPF. If so, it checks to see if a DR and BDR are present. Hello, RID = 1.1.1.2 I see 1.1.1.1 and 1.1.1.3 RID 1.1.1.3 RID 1.1.1.1 RID 1.1.1.2 31. OSPF Advertising a New Network DR BDR New router *The new router sends LSAs about networks to the DR and BDR via the 224.0.0.6 (all DRs) multicast address. LSA 224.0.0.6 RID 1.1.1.3 RID 1.1.1.1 RID 1.1.1.2 32. OSPF Updating Peers about a Network Change DR BDR LSA 224.0.0.5 *The DR sends an update to all routers about the new network learned. It waits for an ACK from all routers. RID 1.1.1.3 RID 1.1.1.1 RID 1.1.1.2 New router 33. OSPF Network Change Flow DR BDR *The DR sends an update to all routers about the network change. It waits for an ACK from all routers. LSA 1 2 3 LSA 224.0.0.6 LSA 224.0.0.5 34. Open Shortest Path First (OSPF) Section 3 Adjacency Case Study 35. Adjacency between rtr4 and rtr5 rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 36. rtr5 Neighbor Discovery OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: f198Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: HELLOPacket Length: 44Network Mask: 255.255.255.252Hello Interval: 10Options: 02Rtr Priority: 1Dead Interval: 40Designated Router : 0.0.0.0Backup Router: 0.0.0.0" rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 1 1 37. Adjacency 2-Way State rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: e98cAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: HELLOPacket Length: 48Network Mask: 255.255.255.252Hello Interval: 10Options: 02Rtr Priority: 1Dead Interval: 40Designated Router : 0.0.0.0Backup Router: 0.0.0.0Neighbor-1: 4.4.4.4" 3 OSPF Version: 2Router Id: 4.4.4.4Area Id: 0.0.0.0Checksum: e98cAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: HELLOPacket Length: 48Network Mask: 255.255.255.252Hello Interval: 10Options: 02Rtr Priority: 1Dead Interval: 40Designated Router : 0.0.0.0Backup Router: 0.0.0.0Neighbor-1: 5.5.5.5" 2 2 3 38. DR Election rtr5 5.5.5.5 4.4.4.4 10.10.0.0/30 .1 .2 10.10.1.4/30 .5 1 2 OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: d575Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: HELLOPacket Length: 48Network Mask: 255.255.255.252Hello Interval: 10Options: 02Rtr Priority: 1Dead Interval: 40Designated Router : 10.10.0.1Backup Router: 10.10.0.2Neighbor-1: 4.4.4.4" OSPF Version: 2Router Id: 4.4.4.4Area Id: 0.0.0.0Checksum: d576Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: HELLOPacket Length: 48Network Mask: 255.255.255.252Hello Interval: 10Options: 02Rtr Priority: 1Dead Interval: 40Designated Router : 10.10.0.1Backup Router: 10.10.0.1Neighbor-1: 5.5.5.5" 1 2 rtr4 39. Adjacency Exstart State rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 1 OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: 7c0eAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: DB_DESCPacket Length: 32Interface MTU: 1500Options: 000042Flags: 7Sequence Num: 77793" OSPF Version: 2Router Id: 4.4.4.4Area Id: 0.0.0.0Checksum: 865eAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: DB_DESCPacket Length: 32Interface MTU: 1500Options: 000042Flags: 7Sequence Num: 75667" 1 2 2 40. Adjacency Exchange State rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 OSPF Version: 2Router Id: 4.4.4.4Area Id: 0.0.0.0Checksum: bfffAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: DB_DESCPacket Length: 192Interface MTU: 1500Options: 000042Flags: 0Sequence Num: 77793Link ID: 4.4.4.4LSA Type: RTRArea ID: 0.0.0.0Router ID : 4.4.4.4Seq. Num: 8000003fAge: 0Length: 72Checksum: 4c64Option Bits Set:E 02... 41. Adjacency Exchange State (continued) rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: 93f9Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: DB_DESCPacket Length: 52Interface MTU: 1500Options: 000042Flags: 1Sequence Num: 77794Link ID: 5.5.5.5LSA Type: RTRArea ID: 0.0.0.0Router ID : 5.5.5.5Seq. Num: 80000003Age: 8Length: 48Checksum: 51b5Option Bits Set:E 02 ... 42. Adjacency Exchange State (continued) OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: 7af8Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: LS_REQPacket Length: 120LS Type: 1Link State Id: 4.4.4.4Advt Router: 4.4.4.4... rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 43. Adjacency Exchange State (continued) rtr5 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 OSPF Version: 2Router Id: 4.4.4.4Area Id: 0.0.0.0Checksum: 1e65Authentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: LS_UPDPacket Length: 100Num of LSAs: 1Link ID: 4.4.4.4LSA Type: RTRArea ID: 0.0.0.0Router ID : 4.4.4.4Seq. Num: 80000040Age: 1Length: 72Checksum: f99cOption Bits Set:E 02# Links: 4Flags:1Link Type: P2P LinkNbr Rtr ID : 2.2.2.2I/F Addr: 10.10.1.1Metric-0: 10002Link Type: Stub NetNetwork: 10.10.1.0Mask: 255.255.255.252Metric-0: 10003Link Type: Stub NetNetwork: 4.4.4.4Mask: 255.255.255.255Metric-0: 04Link Type: TransitDR IP Addr : 10.10.0.1I/F Addr: 10.10.0.2Metric-0: 1000 44. Adjacency Full Adjacency State rtr5 rtr4 5.5.5.5 4.4.4.4 10.10.1.0/30 .1 .2 10.10.1.4/30 .5 OSPF Version: 2Router Id: 5.5.5.5Area Id: 0.0.0.0Checksum: 678dAuthentication: NullAuthentication Key: 00 00 00 00 00 00 00 00Packet Type: LS_ACKPacket Length: 44Link ID: 4.4.4.4LSA Type: RTRArea ID: 0.0.0.0Router ID : 4.4.4.4Seq. Num: 80000040Age: 1Length: 72Checksum: f99cOption Bits Set:E 02... 45. Open Shortest Path First (OSPF) Section 4 OSPF Areas, Networks, and LSAs 46.

Why Areas?

In a large enterprise with many routers and networks, the LSDB and

routing tables become large. This is not advantageous because:

Large routing tables consume memory and result in more CPU cycles

being needed to make a forwarding decision.

Large LSDBs consume memory.

The processing of LSAs is CPU-intensive.

Dividing the network into OSPF areas can reduce these undesirable side

effects.

Advantages

Some advantages of implementing OSPF areas are as follows:

Routers internal to the area incur less overhead.

The impact of a topology change is localized to the area in which it

occurs. Although the change is advertised outside the area, the

processing of LSA, and consequent modification of the SPF tree,

requires less CPU overhead.

With careful network address planning, networks within an area can be

advertised in the form of a summary. This reduces the amount of

processing on all routers external to the area, as well as reducing the

size of the routing table.

47. OSPF Area Overview Area 0 Area 1 Area 2 Autonomous System

Areas allow for summarization

Reduced flooding of topology changes

Hierarchal topology design

RTR-A RTR-B RTR-C RTR-D RTR-E 48. OSPF Types of Routers Area 0 Area 1 Area 2 Autonomous System

RTR-A is a backbone router.

RTR-B and RTR-C are ABRs.

RTR-D and RTR-E are intra-area routers .

RTR-A RTR-B RTR-C RTR-D RTR-E 49. OSPF Link-State Advertisement Types Link-state type 1 2 3 4 5 7 8 9, 10, 11 OSPF function Router link states Network link states Summary link states ASBR link state External link advertisement NSSA external link state External attributes for BGP Opaque LSA 50. OSPF Type 1 (Router) LSA

Each router in an area generates a router LSA for each area it belongs to.

Lists directly attached links

Advertised with the IP prefix and mask assigned to link

Sourced by the RID of the originating router

Flooded within the area only; does not leave the area

Advertised by all OSPF routers

51. OSPF Type 2 (Network) LSA

One LSA for each broadcast or NBMA network in an area

Lists the subnet mask of the link and all attached routers

Advertised by the DR

Flooded within the area only; becomes a type 3 LSA on exit

DR 52.

Floods summary network information to other areas

States the network number and mask

Advertised by the originating area ABR

Goes to all areas within the autonomous system

OSPF Type 3 (Summary) LSA Area 1 Area 0 53.

Stub area

A stub area is configured at the edge of the OSPF routing domain and has

only one ABR. A stub area does not receive LSAs for routes outside its

area, reducing the size of its link state database. A packet destined outside

the stub area is routed to the ABR, which examines it before forwarding

the packet to its destination. The network behind a passive interface is

treated as a stub area, and does not form adjacencies. It is advertised into

the OSPF area as an internal route.

Not so stubby area (NSSA)

A not so stubby area prevents the flooding of external LSAs into the area

by replacing them with a default route. An NSSA can import small stub

(non-OSPF) routing domains into OSPF. Like stub areas, NSSAs are at the

edge of an OSPF routing domain. Non-OSPF routing domains are attached

to the NSSAs, forming NSSA transit areas. Accessing the addressing

scheme of small stub domains permits the NSSA border router to also

perform manual aggregation.

54. OSPF Stub and Stub, No Summary

Stub area (a single area that is a dead end):

The ABR blocks all type 5 LSAs and sends the default route.

RFC-based implementation

Stub area, no summary;

The common industry term is totally stubby.

The ABR blocks all type 3, 4, and 5 LSAs and sends the default route.

Area 0 Area 2 Stub No type 3, 4, or 5 LSA; default route instead No type 5 LSA5; default route instead Area 1 Stub, no summaries 55. OSPF LSA Sequence Numbers

Each sequence number is a 32-bit value represented as a hex number.

The sequence number -N (0x80000000) is reserved (and unused). This leaves N + 1 (0x80000001) as the smallest number (oldest information).

Sequence numbers increment each time an LSA is flooded for that specific network.

The higher the sequence number, the more trusted the information.

The counters roll over when the maximum value is reached.

56. OSPF Packet Processing

Dealing with topology changes in a router:

Is entry inLSDB? Sequence No. same? End No No No Yes Yes Yes LSU/LSA Ignore Add to LSDB Send ACK Flood LSA Run SPF Is sequencenumber higher than in LSDB? Send LSU backwith newerinformation 57.

Virtual links and OSPF:

Designed for non-contiguous areas

Overcomes the requirement that all areas directly connect to Area 0

Not a good permanent fix to a problem

OSPF Defining Virtual Links Area 1 Area 0 Area 4 RID 1.1.1.1 RID 2.2.2.2 Virtual link 58.

Passive interface

The objective of the passive interface is to enable an interface to advertise

into an OSPF domain while limiting its adjacencies.

When changing the interface type value to passive, it is advertised into the

OSPF domain as an internal stub network with the following behaviors:

does not send hello packets into the OSPF domain

does not receive hello packets from the OSPF domain

does not form adjacencies in the OSPF domain

Circuitless IP

Circuitless IP (CLIP) is a virtual (or loopback) interface that is not associated with anyphysicalport. You can use the CLIP interface to provide uninterrupted connectivity to your switchas long as there is an actual path to reach the device .

59. Open Shortest Path First (OSPF) Section 5 OSPF Implementation 60. We can findout what is wrong from trace level 6 3 output : ers8600 :5/trace# level 6 3 ers8600 :5/trace# clear ers8600 :5/trace# info 61.

Passport-8610:5/trace# info tail

os_dbp.c: 463 : SendDDPacket: nbr_ipa=47.163.245.1

os_lsd.c: 572 : ospfFindLsai: lsid=0.0.0.0 rtid=139.177.189.1 area=0.0.0.0 type=5

os_recv.c : 1765: ospfProcDDP: process_db_desc_packet_contents ipa=47.163.245.11

os_recv.c : 1524: ospfProcDDP: starting to process ddpacket nbr=47.163.245.1

os_recv.c : 1314: ProcDDP: nbr=139.177.189.1 seq 2fa3f50c

os_recv.c : 1303: ospfProcDDP: state= EXCHANGE

os_dbp.c: 541 : SendDDPacket: sending ddpkt nbr_rtid=139.177.189.1 seq=2fa3f50b

os_recv.c : 1765: ospfProcDDP: process_db_desc_packet_contents ipa=47.163.245.11

os_recv.c : 1390: ospfProcDPP: starting to process ddpacket nbr=47.163.245.1

os_neigh.c: 374 : nbr_change_state: rtid=139.177.189.1 ipa= 47.163.245.1EX_START->EXCHANGE

os_neigh.c: 289 : nbr_change_state: rtid=139.177.189.1 nbr_ipa=47.163.245.1 state= EXCHANGE

os_neigh.c: 1080: ospf_do_negotiation_done: nbr=47.163.245.1

os_recv.c : 1374: ospfProcDDP: settingthis end to slave modeipa= 47.163.245.11

os_recv.c : 1314: ProcDDP: nbr=139.177.189.1 seq 2fa3f50b

os_recv.c : 1303: ospfProcDDP: state= EX_START

os_dbp.c: 541 : SendDDPacket: sending ddpkt nbr_rtid=47.163.245.97 seq=00012173

os_neigh.c: 374 : nbr_change_state: rtid=47.163.245.97 ipa= 47.163.245.62WAY->EX_START

os_neigh.c: 289 : nbr_change_state: rtid=47.163.245.97 nbr_ipa=47.163.245.6 state= EX_START

os_neigh.c: 1294: ospf_do_adj_ok: nbr=47.163.245.1

os_intf.c : 590 : ospfElectDR: ipa=47.163.245.11 IfStateChange PTPT->DR_OTHER

os_recv.c : 1338: ospfProcDDP: nbrstate(2WAY) dropping ddpacket ipa= 47.163.245.11

os_recv.c : 1314: ProcDDP: nbr=139.177.189.1 seq 2fa3f50b

os_recv.c : 1303: ospfProcDDP: state=2WAY

os_neigh.c: 374 : nbr_change_state: rtid=139.177.189.1 ipa= 47.163.245.1INIT->2WAY

os_neigh.c: 289 : nbr_change_state: rtid=139.177.189.1 nbr_ipa=47.163.245.1 state= 2WAY

os_neigh.c: 1012: ospf_do_two_way: nbr=47.163.245.1

os_neigh.c: 374 : nbr_change_state: rtid=139.177.189.1 ipa= 47.163.245.1DOWN->INIT

os_neigh.c: 289 : nbr_change_state: rtid=139.177.189.1 nbr_ipa=47.163.245.1 state= INIT

os_neigh.c: 954 : ospf_do_hello_received: nbr=47.163.245.1

os_hello.c: 577 : ospfSendHelloPacket: ipa=47.163.245.11 cnt=7571

os_neigh.c: 374 : nbr_change_state: rtid=139.177.189.1 ipa= 0.0.0.0NULL->DOWN

os_neigh.c: 289 : nbr_change_state: rtid=139.177.189.1 nbr_ipa=0.0.0.0 state= DOWN

63. verify_ospf_packet:area mismatch other_areaid =0.0.0.1 my_areaid=0.0.0.0 ospf_recv: verify_ospf_packetreturned error src=47.163.245.1 pkt type=1 ospfProcHello: received on ipa=47.163.245.11 src_ipa=47.163.245.1 ospfProcHello:hello-interval mismatchipa=47.163.245.11 other_int=5,my_int=10 ospfProcHello: received on ipa=47.163.245.11 src_ipa=47.163.245.1 ospfProcHello:dead-router mismatchipa=47.163.245.11 , other_int=30, my_int=40 verify_ospf_packet:authType mismatch ipa= 47.163.245.11 ospf_recv: verify_ospf_packet returned error src=47.163.245.1 pkt type=1 Configuration problems detected in the Log 64.

Inactivity timer expired in the Log

NeighborInactivityFunc:processing the nbr inactivity timerfor ipa=47.163.245.1

nbr_change_state: rtid=139.177.189.1 nbr_ipa=47.163.245.1 state=DOWN

nbr_change_state: rtid=139.177.189.1 nbr_ipa=47.163.245.1FULL->DOWN

ospfElectDR: ipa=47.163.245.11 IfStateChange from DR_OTHER->DR

Passport-8610:5# show ip ospf info

================================================================================

Ospf General

================================================================================

RouterId: 45.175.216.0

AdminStat: enabled

VersionNumber: 2

AreaBdrRtrStatus: true

ASBdrRtrStatus: true

ExternLsaCount: 11

ExternLsaCksumSum: 303255(0x4a097)

TOSSupport: 0

OriginateNewLsas: 58

RxNewLsas: 47

TrapEnable: false

AutoVirtLinkEnable: false

SpfHoldDownTime: 10

Passport-8610:5# show ip ospf stat

================================================================================

Ospf Statistics

================================================================================

NumBufAlloc: 6878

NumBufFree: 6878

NumBufAllocFail: 0

NumBufFreeFail: 0

NumTxPkt: 6885

NumRxPkt: 897

NumTxDropPkt: 0

NumRxDropPkt: 0

NumRxBadPkt: 12092

NumSpfRun: 17

LastSpfRun: 0x6642e8

LsdbTblSize: 16

NumAllocBdDDP: 3

NumFreeBdDDP: 3

NumBadLsReq: 0

NumSeqMismatch: 0

67. 68.

Passport-8610:5# show ip ospf inter

================================================================================

Ospf Interface

================================================================================

INTERFACEAREAIDADM IFST MET PRIO DR/BDRTYPE AUTHTYPE

--------------------------------------------------------------------------------

139.177.100.110.0.0.0enDR101139.177.100.11brdc none

0.0.0.0

47.163.245.110.0.0.0enBDR10147.163.245.6brdc none

47.163.245.11

Passport-8610:5# show ip ospf ifsta ts

================================================================================

Ospf Interface Statistics

================================================================================

---HELLOS---- ---DBS--- -LS REQ-- --LS UPD--- --LS ACK---

INTERFACERXTXRXTXRXTXRXTXRXTx

--------------------------------------------------------------------------------

47.163.245.118076466810233514331

139.177.100.11035900000000

69. 70. Passport-8610:5# show ip ospf nei================================================================================ Ospf Neighbors ================================================================================ INTERFACENBRROUTERIDNBRIPADDRPRIO_STATERTXQLEN PERMANENCE -------------------------------------------------------------------------------- 47.163.245.11139.177.189.147.163.245.11Full0Dynamic47.163.245.1147.163.245.9747.163.245.61Full0DynamicDone Passport-8610:5# show ip ospf area ================================================================================ Ospf Area ================================================================================ AREA_IDSTUB_AREANSSAIMPORT_SUM ACTIVE_IFCNT-------------------------------------------------------------------------------- 0.0.0.0falsefalsetrue20.0.0.1truefalsetrue0STUB_COST SPF_RUNSBDR_RTR_CNT ASBDR_RTR_CNT LSA_CNTLSACK_SUM-------------------------------------------------------------------------------- 012225118184180000 71. 72.

Passport-8610:5# show ip ospf lsdb

================================================================================

Ospf Lsdb

================================================================================

Router Lsas in Area 0.0.0.0

LSTYPELINKSTATEIDADV_ROUTERAGESEQ_NBRCSUM

--------------------------------------------------------------------------------

Router45.175.216.045.175.216.09700x80000008 0xbabb

Router47.163.245.9747.163.245.974100x800000ff 0x68f8

Router139.177.189.1139.177.189.14240x800004fe 0xcb2

Network Lsas in Area 0.0.0.0

--------------------------------------------------------------------------------

Network47.163.245.647.163.245.974100x80000004 0x217c

Summary Lsas in Area 0.0.0.0

--------------------------------------------------------------------------------

Summary10.0.0.047.163.245.971310 0x800000e7 0x7bc7

73. Passport-8610:5# show ip ospf lsdb lsatype 1 detail Router Link LSA : Area: 0.0.0.0 (0x0) Age: 1011 Opt: true (External Routing Capability) Type: 1 LsId: 45.175.216.0 (0x2dafd800) Rtr: 45.175.216.0 Seq: -2147483640 (0x80000008) Csum: 47803 (0xbabb) Len: 48 ABR: true ASBR: true Vlnk: false (endpoint of active Vlink) #Lnks:1 [1] Id: 139.177.100.0 (0x8bb16400) Data: 255.255.255.0 (0xffffff00) Type: (conn-to-stub-net)(Id=Subnet-Prefix, Data=Prefix-Len) #Tos: 0Met: 10 74.

Useful Commands

1To verify that OSPF is enabled on the local router and on the

neighbor router, enter the following CLI command:

show ip ospf info

enter the following NNCLI command:

show ip ospf

Also, from the command output, verify that the router IDs are

different on the local router and the neighbor router.

2To verify that OSPF is enabled on the local router interface and

the neighbor router interface, enter the following command using

the CLI or NNCLI:

show ip ospf interface

Also, from the command output, verify that the OSPF interfaces

are not configured as passive interfaces.

3To verify the reachability of the neighbor, enter the following

command using the CLI or NNCLI:

4To verify the reachability of the neighbor through the

allSPFRouters address, enter the following CLI command (and

see whether the neighbor responds):

ping 224.0.0.5

5Verify that the following parameters are configured to the

same values on both interfaces: subnet, hello interval, and

dead interval. To display these parameters, enter the following

show ip ospf int-timers

6Verify that the following parameters are configured to the same

values on both interfaces: area ID, area type (for example, stub

or NSSA). To display these parameters, enter the following

show ip ospf area

7Verify that configured access lists are not affecting OSPF or IP

traffic between the neighbors. To display the ACL configuration,

enter the following command using the CLI or NNCLI:

show filter acl config

76. Diagnosing OSPF neighbor state problems

At initial startup, routers transmit hello packets in an attempt to find other OSPF routers with which form adjacencies. After the hello packets are received, the routers perform an initialization process, which causes the routers to transition through various states before the adjacency ise stablished .

Neighbor states

Step State Description

1 Down : Indicates that a neighbor was configured manually,

but the router did not received any information from

the other router. This state can occur only on NBMA

interfaces.

2 Attempt : On an NBMA interface, this state occurs when the

router attempts to send unicast hellos to any configured

interfaces.

3 Init : The router received a general hello packet (without its

Router ID) from another router.

4 2-Way : The router received a Hello directed to it from another

router. (The hello contains its Router ID.)

5 ExStart : Indicates the start of the Master/Slave election process.

6 Exchange : Indicates the link state database (LSDB) is exchanged

7 Loading : Indicates the processing state of the LSDB for input

into the routing table. The router can request LSA for

missing or corrupt routes.

8 Full : Indicates the normal full adjacency state

Problems with OSPF occur most often during the initial startup, when the

router cannot form adjacencies with other routers and the state is stuck in

the Init or ExStart/Exchange state.

Init state problems

A router can be stuck in Init state and not form an adjacency. There are

several possible causes for this type of problem:

Authentication mismatch or configuration problem

There could be a mismatch in authentication keys or both sides are not

configured for authentication.

To determine if this is causing the problem, issue thetrace Level 6 2

command, which allows you to see the OSPF packets that are received:

ERS-8606:5#trace level 6 2

ERS-8606:5#trace screen on

The following example shows the error received when there is an

authentication failure:

[03/24/03 15:55:07:216] tMainTask OSPF: os_recv.c : 710 :

verify_ospf_packet: authType mismatch ipa= 10.1.1.18

Access Lists implemented on routers

Ensure that the path is not reachable due to access lists implemented on routers:

Ensure the multicast address of 224.0.0.5 is able to traverse the link.

If multicast traffic is being blocked for some reason, you must to configure the Ethernet Routing Switch 8600 for OSPF nonbroadcast multiaccess area (NBMA), instead of Broadcast.

ExStart/Exchange problems

Although both routers can recognize each other and have moved beyond 2-way, the routers could be stuck in the ExStart/Exchange state. A mismatch in maximum transmission unites (MTU) sizes between the routers usually causes this type of problem. For example, one router could be set for a high MTU size and the other routers default value is a smaller value. Depending on the size of the LSDB, the router with the smaller value may not be able to process the larger packets and thus be stuck in ExStart/Exchange state. To avoid this problem, ensure that the MTU size

value for both routers match. This problem is usually encountered during interoperations in networks with other vendor devices. Use thetrace level 6 2command to help troubleshoot this type of problem

Incoming OSPF database description (DBD) packets are dropped if their MTU size is greater than 1500 bytes. To allow the Ethernet Routing Switch 8600 to accept OSPF DBD packets with a different MTU size, enable mtu-ignore using the following command:

ERS-8606:5#config ip ospf interface mtu-ignore

ipaddris the IP address of the OSPF interface.

enable|disableenables or disables the feature.

8600 Feature Matrix

Notes :

Router ID need to be different from any physical IPs.

At the ERS 5510, a specific configuration need to be done :

ip ospf op-mode 5510

ERS5500 series and ers 8300 need advanced license to configure OSPF.

ATTENTION

The Nortel Ethernet Routing Switch 5000 Series implementation of OSPF only

supports broadcast and passive interfaces. Point-to-point and NBMA interfaces

are not supported.

83. Important Points at OSPF

Interfaces which do not need to run the routing protocol, should be kept as externals. OSPF Announce Policies must then be applied to import RIP and local routes into the OSPF LSDB.

OSPF Passive interfaces are OSPF internal routes without forming adjacencies. No OSPF hellos are sent.

OSPF route summarization and black hole routes

When you create an OSPF area route summary on an area boundary router (ABR), be aware that the summary route can attract traffic to the ABR that it does not have a specific destination route for. If you have enabled ICMP unreachable message generation on the switch, this may result in a high CPU utilization rate.

To avoid such a scenario, Nortel recommends that you use a black hole static route configuration. The black hole static route is a route (equal to the OSPF summary route) with a next hop of 255.255.255.255. This ensures that all traffic that does not have a specific next hop destination route in the routing table is dropped by the hardware.

ERS5510 Known Limitations :

Q01839838 : Question / ERS5510 v5.1 / 512 route limitation - Failed route add

Layer 3 Scaling Limitations

- Up to 512 routes (local + static + dynamically learned).The 5510 can support up to 512 routes, although in some instances the 5510 may only be able to scale to 64 routes depending on address distribution/sequence.However, any 5510 configuration supports a minimum of 64 routes, and in most cases will support many more routes (that is, up to 512).Nortel always supports the default route.The 5520 and 5530 also support 512 routes, and testing indicates that more than 512 routes are possible in some configurations, although 512 is the officially supported limit.

1) Regarding the statement "The 5510 can support up to 512 routes, although in some instances the 5510 may only be able to scale to 64 routes depending on address distribution/sequence.", are there any other factors that may limit the number of learned routes to 64.

WorkAround :OSPF Route Summarization : Knova solution 8198646

In a situation likethe above network,OSPF (Open Shortest Path First)routes can be summarized to reduce the routing table.

To distribute local attached interfaces into OSPF as a summary on the ERS (Ethernet Routing Switch) 8600 the following steps need to be performed. In this topology ERS 8600will send the static routes to ERS 5510:

The below processes must be done : - Configuration of the ERS 8600 to be an ASBR (Autonomous System Border Router) - Creation of a policy that matches to the locally attached interfaces and distributes a summary - Configuration of the OSPF redistribution entry To summarize the routes,the local attached interfaces must not run OSPF.

In this example below the 3 local attached interfaces 192.168.4.0/24, 192.168.5.0/24 and 192.168.6.0/24 will be advertised as 192.168.0.0/16 into OSPF.

Configure the VLANs (Virtual LAN)192.168.4.0,192.168.5.0 and 192.168.6.0 all with mask 24 vlan 4 create byport 1 vlan 4 ports add 2/4 member portmember vlan 4 ip create 192.168.4.173/255.255.255.0 vlan 5 create byport 1 vlan 5 ports add 2/5 member portmember vlan 5 ip create 192.168.5.173/255.255.255.0 vlan 6 create byport 1 vlan 6 ports add 2/6 member portmember vlan 6 ip create 192.168.6.173/255.255.255.0

Aprefix list for all 192.168.x.x networks with a mask of 24 Networks with a mask of e.g. 17 or 30 (such as 192.168.7.1/30) will not be covered with this prefix In this case the "mask length from" and "mask length to" would need to be adjusted Ip prefix-list "192.168.0.0_16-24-24" add-prefix 192.168.0.0/16maskLenFrom 24 maskLenTo 24 This is the prefix to advertise 192.168.0.0/16 as a summary ip prefix-list "192.168.0.0_16-16-16" add-prefix 192.168.0.0/16maskLenFrom 16 maskLenTo 16 Create a policy ip route-policy "thePolicy" seq 10 create ip route-policy "thePolicy" seq 10 enable ip route-policy "thePolicy" seq 10 match-network "192.168.0.0_16-24-24" ip route-policy "thePolicy" seq 10 set-injectlist "192.168.0.0_16-16-16" General OSPF Config ip ospf admin-state enable The router needs to be ASBR ip ospf as-boundary-router enable ip ospf enable The redistribution policy ip ospf ip ospf redistribute direct metric 10 ip ospf redistribute direct route-policy "thePolicy" ip ospf redistribute direct enable

88. Before the summarization ip routes for 192.168.4.0, 192.168.5.0, 192.168.6.0 are seen as separately as below: 5510-24T#show ip route =============================================================================== Ip Route =============================================================================== DST MASK NEXT COST VLAN PORT PROT TYPE PRF ------------------------------------------------------------------------------- 0.0.0.0 0.0.0.0 47.168.65.1 10 1 T#1 S IB 5 10.10.10.0 255.255.255.0 10.10.10.53 1 10 ---- C DB 0 47.168.65.0 255.255.255.0 47.168.65.53 1 1 ---- C DB 0 192.168.4.0 255.255.255.0 10.10.10.173 20 10 10 O IB 20 192.168.5.0 255.255.255.0 10.10.10.173 20 10 10 O IB 20 192.168.6.0 255.255.255.0 10.10.10.173 20 10 10 O IB 20 Total Routes: 6 ------------------------------------------------------------------------------- TYPE Legend: I=Indirect Route, D=Direct Route, A=Alternative Route, B=Best Route, E=Ecmp Rou te, U=Unresolved Route, N=Not in HW 89.

after route summarization routing table will be as below all the 192.168.4.0, 192.168.5.0, 192.168.6.0 routes will be seen in192.168.0.0

5510-24T#show ip route

===============================================================================

Ip Route

===============================================================================

DST MASK NEXT COST VLAN PORT PROT TYPE PRF

-------------------------------------------------------------------------------

0.0.0.0 0.0.0.0 47.168.65.1 10 1 T#1 S IB 5

10.10.10.0 255.255.255.0 10.10.10.53 1 10 ---- C DB 0

47.168.65.0 255.255.255.0 47.168.65.53 1 1 ---- C DB 0

192.168.0.0 255.255.0.0 10.10.10.173 1 10 10 O IB 125

Total Routes: 4

-------------------------------------------------------------------------------

TYPE Legend:

I=Indirect Route, D=Direct Route, A=Alternative Route, B=Best Route, E=Ecmp Rou

te, U=Unresolved Route, N=Not in HW

Q01828889 :ERS5500 - OSPF adjacencies fail when 'Unknown Multicast Filter' enabled

WorkAround :Configure ip igmp mrouter between the ospf vlan.

5.1 Load Known Limitations :

Q01832726:In a SuperMezz R mode HA-CPU system configured with a dead interval of 3 seconds, when the Master is removed, OSPF neighborship is lost for interfaces configured with low timers (for example, 1 s Hello and 3 s Dead Interval). If failover is triggered by soft-resetting the Master CPU, or the dead interval is 10 s, this issue does not occur.

Workaround:Remove the Master CPU during a maintenance window or other low-traffic periods. Or, increase the dead-interval to 10 s.

Q01735063: When the Link Aggregation Control Protocol (LACP) adds a new port to a link aggregation group (LAG), it brings all the ports of the LAG down, which brings the entire interface down. As a result, the multilink trunk is deleted and the VLAN interface is deleted. This causes OSPF to go down.

Q02008788: In a square SMLT environment, if OSPF is disabled and re - enabled while the IST is down, the OSPF adjacency to one of the non-IST peer boxes may show ExStart state for 5 to 8 minutes. The condition does clear itself in that time frame, and will go to full adjacency.

HA Feature with OSPF

HA-CPU for Layer 3 redundancy avoids disruption of network traffic when a

master CPU that is running OSPF fails over. It maintains an exact copy of

the OSPF instance of the master CPU on the HA-CPU. When the HA-CPU

initializes, all OSPF information on the master CPU is Table Synchronized

and all OSPF events are Event Synchronized to the HA-CPU. When a

master CPU failover occurs, the OSPF instance on HA-CPU resumes

without affecting router traffic and OSPF neighbors.

During HA-CPU to master CPU transition, it can take up to 3 seconds for the

new master CPU to transmit OSPF packets. Therefore, Nortel recommends

router dead intervals of 5 seconds or higher. (this value is for 8692SF)

93. OSPF MTU Size Problem Network AB Down Two way received Init Down Init Hello received Two way received Hello received ExStart ExStart Negotioation done Negotioation done Exchange Exchange Router A Router B Neighbor State Neighbor State (Packet too large, dropped) Sequence numbermismatch ExStart ExStart Sequence number mismatch (Timeout expired) Hello (DR = B, seen = 0) Hello(DR = 0, seen = 0) Hello (DR = B, seen = A) Hello(DR = B, seen = B) Database Descr. (Seq = Y , Init, Master) Database Descr. (Seq = X , Init, Master) DD (Seq = Y , More, Slave) DD (Seq = Y+1 , Master) Retransmitted DD (Seq = Y , More, Slave) Database Descr. (Seq = Z ,Init , Master) 94. Global OSPF Parameters 95.

TrapEnable- Indicates whether or not traps relating to the Spanning. Tree Protocol should be sent for this STG.

AutoVirtLinkEnable- Enables or disables automatic creation of virtual links.

SpfHoldDownTime- Allows the user to change the OSPF Hold Down timer value (3 to 60 seconds).

LastSpfRun- Indicates the time (SysUpTime) since the last SPF calculated by OSPF.

SPF Run -Allows you to initiate a new SPF run to update the routing table. This feature can be used when you need to immediately restore a deleted OSPF-learned route. It can also be used as a debug mechanism when the routing tables entries and the link-state database are out of sync.

Enable- Enables (true) or disables (false) OSPF on the port.

HelloInterval- The length of time, in seconds, between the Hello

packets that the router sends on the interface. This value must be the

same for all routers attached to a common network.

RtrDeadInterval- The number of seconds that a routers Hello packets

have not been seen before its neighbors declare the router down. This

should be some multiple of the Hello interval. This value must be the

same for all routers attached to a common network.

DesigRtrPriority- The priority of this interface. In multi-access

networks, this field is used in the designated router election algorithm.

The value 0 signifies that the router is not eligible to become the

designated router on this particular network. In the event of a tie in this

value, routers will use their router ID as a tiebreaker. The router with

the highest ID wins.

Metric- The metric of using this type of service on this interface. The

default value of the TOS 0 Metric is 10^8 / ifSpeed. The value FFFF is

distinguished to mean no route via this TOS.

AuthKey- The Authentication Key. If the areas authorization type is

simplePassword, and the key length is shorter than 8 octets, the agent

will left-adjust and zero-fill to 8 octets. When read, ospfIfAuthKey

always returns an octet string of length zero. The key may be entered

as ASCII text.

AreaID- The identification number for the area, typically formatted as

an IP address.

IfType- When you enable an OSPF interface, you designate it as a

broadcast (active), non-broadcast multiaccess (NBMA) or passive

interface. When an OSPF interface is enabled, you cannot change its

interface type. You must first disable the interface. You can then

change its type and re-enable it. If it is an NMBA interface, you must

also first delete its manually configured neighbors.

PollInterval- Length of time, in seconds, between hello packets sent to

an inactive OSPF router.

98. Open Shortest Path First (OSPF) Section 6 OSPF Implementation Lab workout 99. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ospf domain Ers 5510 Mgmt 47.168.90.168 nssa Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations Vlan 192.168.4.x/24 Vlan 192.168.5.x/24 Vlan 192.168.6.x/24 ---------------------------Direct routes------------------------------ 10.10.10.x/24 10.11.13.x/24 10.12.19.x/24 Nssa impl. Summurized and injected to ospf 100. OSPF Implementation Nssa impl. 101. OSPF Implementation Nssa impl. 102. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ospf domain Ers 5510 Mgmt 47.168.90.168 mport no external Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations Vlan 192.168.4.x/24 Vlan 192.168.5.x/24 Vlan 192.168.6.x/24 ---------------------------Direct routes------------------------------ 10.10.10.x/24 10.11.13.x/24 10.12.19.x/24 mport no external impl. Summurized and injected to ospf 103. OSPF Implementations Import noexternal impl. 104. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ospf domain Ers 5510 Mgmt 47.168.90.168 mport no external Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations Vlan 192.168.4.x/24 Vlan 192.168.5.x/24 Vlan 192.168.6.x/24 ---------------------------Direct routes------------------------------ 10.10.10.x/24 10.11.13.x/24 10.12.19.x/24 No area summary Import noexternal && no area summary impl. (Totally stubby area) Summurized and injected to ospf 105. OSPF Implementations Import noexternal && no area summary impl. (Totally stubby area) 106. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ers 5510 Mgmt 47.168.90.168 Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations Vlan 192.168.4.x/24 Vlan 192.168.5.x/24 Vlan 192.168.6.x/24 -------------------Direct routes--------------------- 10.100.10.x/24 10.11.13.x/24 10.12.19.x/24 nssa Not so stubby area 2. Impl. Summurized and injected to ospf 107. 108. 109. QUESTIONS & COMMENTS 110. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ers 5510 Mgmt 47.168.90.168 Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations 192.168.4.x/24 192.168.5.x/24 192.168.6.x/24 10.100.10.x/24 10.11.13.x/24 10.12.19.x/24 nssa Area aggregation 111. 112. ERS8600 Mgmt 47.168.90.157 area0 area1 Ers5510 Mgmt 47.168.65.53 area2 Ers 5510 Mgmt 47.168.90.168 Ers5510 Mgmt 47.168.90.167 Ers5510 Mgmt 47.168.90.142 Ers5510 Mgmt 47.168.90.143 Ers5510 Mgmt 47.168.90.145 OSPF Implementations 192.168.4.x/24 192.168.5.x/24 192.168.6.x/24 10.100.10.x/24 10.11.13.x/24 10.12.19.x/24 nssa Area aggregation 10.10.19.x/24 113. 114.

Thanks

115. Sources

Juergen Arlt documents

Alcatel Lucent Documents

Nortel Networks Documents

Ospf

Documents

ospf authentication

ospf area

ospf path determination

ospf multicast

ospf adjacencies

ospf packet header

ospf section

ospf overview