Open Shortest Path First OSPF (Part 2) George Macri 6 th CEENET Workshop, Budapest 2000

Interior IP Routing Protocols Routing Information Protocol (RIP) Interior Gateway Routing Protocol (IGRP) Open Shortest Path First (OSPF) Protocol Enhanced IGRP (EIGRP) Routing Information Protocol (RIP) Interior Gateway Routing Protocol (IGRP) Open Shortest Path First (OSPF) Protocol Enhanced IGRP (EIGRP) Application Transport Internet Network Interface Hardware

IP Routing Configuration Tasks Network IGRP, RIP Global configuration Select routing protocol(s) Network Network Specify network(s)

IP Routing Configuration Tasks Network Network IGRP, RIP Network RIP Global configuration Select routing protocol(s) Specify network(s) Interface configuration Verify address/subnet mask

Defines an IP routing protocol router protocol [ keyword ] Router (config) # Dynamic Routing Configuration network network-number Router (config-router) # The network subcommand is a mandatory configuration command for each IP routing process

CONFIGURING OSPF

Router (config) # router ospf process-id OSPF Basic Configuration Commands Enables an OSPF routing process Router (config-router) # network address wildcard-mask area area-id Selects participating interfaces

OSPF Basic Configuration Example router ospf 63 network area 1 network area 0 network area 1 Area 0 Area E1 T0 E E2

Minimizes routing table entries Localizes impact of a topology change OSPF Route Summarization Area 0 Backbone ABRs Area 1 Summarization xx

O O O O O O O Routing Table for B Routing Table for C IA Inter-area (IA) summary link carries mask One entry can represent several subnets Route Summarization (cont.) Area 1 Area 0 ABR Summarization B AC

Summary Route Mask = 240 Address = 12 Existing Subnet Mask = 252 Address = Valid 3rd Subnet Invalid Subnet Zero Some addresses may need reallocating Route Summarization Issue

Router (config-router) # area area-id range address mask Route Summarization Commands Consolidates IA routes on an ABR Router (config-router) # summary-address address mask Consolidates external routes on an ASBR

Route Summarization Example R2 R2# router ospf 100 network area 2 network area 0 area 0 range area 2 range R1# router ospf 100 network area 1 network area 0 area 0 range area 1 range Area Area Interface Addresses ( mask) R1 R2 Area 0

Allows routing-information exchange between OSPF and other routing protocols OSPF Route Redistribution OSPF RIP IGRP Enhanced IGRP IS-IS BGP EGP

Router (config-router) # redistribute protocol [ process-id ] [ metric value ] [ metric-type value ] [ subnets ] OSPF Redistribution Command Redistributes routes from OSPF into other routing protocols (and vice versa)

OSPF Redistribution Example 1 Redistribution between RIP and OSPF RIP OSPF Area 0 S0 S1 R1

OSPF Redistribution Example 1 router ospf 109 network area 0 network area 0 redistribute rip subnets metric-type 1 metric 20 router rip network passive-interface serial 0 passive-interface serial 1 default-metric 10 redistribute ospf 109 match internal external 1 external 2

Redistribution Example 2 "Back door" creates potential loop RIP OSPF Area 0 RIP Avoiding Loops R2 R3 R2 R1

Redistribution Example 2 cont router ospf 109 network area 0 network area 0 redistribute rip subnets metric-type 1 metric 20 distribute-list 11 out rip access-list 11 permit

VERIFYING OSPF OPERATION

Verifies interfaces are in correct areas Router# show ip ospf interface e 0 Ethernet0 is up, line protocol is up Internet Address , Area Process ID 10, Router ID , Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) , Interface address Backup Designated router (ID) , Interface address Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 0:00:02 Neighbor Count is 3, Adjacent neighbor count is 3 Adjacent with neighbor (Designated Router) Loopback0 is up, line protocol is up Internet Address , Area 1 Process ID 10, Router ID , Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host show ip ospf interface Command

Displays general information about the OSPF routing process Router # show ip ospf Routing Process "ospf 1" with ID Supports only single TOS (TOS0) routes SPF schedule delay 5 secs, Hold time between two SPFs 10 secs Number of areas in this router is 1 Area 23 Number of interfaces in this area is 3 Area has no authentication SPF algorithm executed 19 times Area ranges are Link State Update Interval is 0:30:00 and due in 0:04:55 Link State Age Interval is 0:20:00 and due in 0:04:55 show ip ospf Command

Router# show ip ospf database OSPF Router with ID ( ) (Process ID 1) Router Link States (Area 23) Link IDADV Router Age Seq# x x B x Checksum 0x80B6 0xE11C 0xE35E Link count x x80A1 1 Net Link States (Area 23) Link ID ADV Router Age Seq# Checksum x x2FCE x xFB29 show ip ospf database Command

Router>show ip protocol Routing Protocol is “ospf 300” Sending updates every 0 seconds Invalid after 0 seconds, hold down 0, flushed after 0 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: ospf 300 Routing for Networks: / / Routing Information Sources: GatewayDistanceLast Update d :17: :17: :17: d :17: :17: d :17: :17: :17:33 Distance: (default is 110) - - More - - show ip protocol Command

Router # show ip ospf virtual-links Other OSPF show Commands Displays parameters about OSPF virtual links Router # show ip ospf neighbor detail Displays neighbor information per interface Router # show ip ospf border-routers Displays routes to the ABR and ASBR