© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configuring OSPF Configuring OSPF Routing

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v router ospf process-id [vrf vpn-name] Router(config)# Enables one or more OSPF routing processes Configuring Basic OSPF network ip-address wildcard-mask area area-id Router(config-router)# Defines the interfaces that OSPF will run on Router(config-if)# ip ospf process-id area area-id [secondaries none] Optional method to enable OSPF explicitly on an interface

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configuring OSPF on Internal Routers of a Single Area

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configuring OSPF for Multiple Areas

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v OSPF Router ID The router is known to OSPF by the OSPF router ID number. LSDBs use the OSPF router ID to differentiate one router from the next. By default, the router ID is the highest IP address on an active interface at the moment of OSPF process startup. A loopback interface can override the OSPF router ID. If a loopback interface exists, the router ID is the highest IP address on any active loopback interface. The OSPF router-id command can be used to override the OSPF router ID. Using a loopback interface or a router-id command is recommended for stability.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Router(config)#interface loopback 0 Router(config-if)#ip address If the OSPF process is already running, the router must be reloaded or the OSPF process must be removed and reconfigured before the new loopback address will take effect. Loopback Interfaces

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v router-id ip-address This command is configured under the router ospf [process-id] command. Any unique arbitrary 32-bit value in an IP address format (dotted decimal) can be used. If this command is used on an OSPF process that is already active, then the new router ID is used after the next reload or manual OSPF process restart using: OSPF router-id Command Router(config-router)# Router(config)#router ospf 1 Router(config-router)#router-id Router#clear ip ospf process clear ip ospf process Router#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v OSPF Router ID Verification RouterB#sh ip ospf Routing Process "ospf 50" with ID Number of areas in this router is 2. 2 normal 0 stub 0 nssa Number of areas transit capable is 0 External flood list length 0 Area BACKBONE(0) Area has no authentication SPF algorithm last executed 00:01: ago SPF algorithm executed 7 times Area 1 Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:00: ago SPF algorithm executed 3 times

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v show ip protocols Router# Verifies the configured IP routing protocol processes, parameters, and statistics Verifying OSPF Operation show ip route ospf [process-id ] Router# Displays all OSPF routes learned by the router show ip ospf interface [type number] Router# Displays the OSPF router ID, area ID, and adjacency information

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v show ip ospf Router# Displays the OSPF router ID, timers, and statistics Verifying OSPF Operation (Cont.) show ip ospf neighbor [type number] [ neighbor-id] [detail ] Router# Displays information about the OSPF neighbors, including DR and BDR information on broadcast networks

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: The show ip route ospf Command RouterA#show ip route ospf /8 is variably subnetted, 3 subnets, 2 masks O IA /24 [110/782] via , 00:03:05, FastEthernet0/0 RouterA#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: The show ip ospf interface Command RouterA#show ip ospf interface fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Internet Address /24, Area 0 Process ID 1, Router ID , Network Type BROADCAST, Cost: 1 Transmit Delay is 1 sec, State DROTHER, Priority 0 Designated Router (ID) , Interface address No backup designated router on this network Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:04 Supports Link-local Signaling (LLS) Index 1/1, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 4 Last flood scan time is 0 msec, maximum is 4 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor (Designated Router) Suppress hello for 0 neighbor(s)

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: The show ip ospf neighbor Command RouterB# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface FULL/DROTHER 00:00: FastEthernet0/ FULL/ - 00:00: Serial0/0/1 RouterB# show ip ospf neighbor detail Neighbor , interface address In the area 0 via interface FastEthernet0/0 Neighbor priority is 0, State is FULL, 16 state changes DR is BDR is Neighbor , interface address In the area 1 via interface Serial0/0/1 Neighbor priority is 0, State is FULL, 6 state changes DR is BDR is

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Summary Configuration of OSPF is a two-step process: –Enter OSPF configuration with the router ospf command. –Use the network command to describe which interfaces will run OSPF in which area. OSPF selects a router ID at startup time: –The router IDs specified in the router-id command under the OSPF process. –Otherwise, the highest IP address of a loopback interface, if there are any, is used. –By default, the highest IP address of all active interfaces Use the show ip ospf command to verify the router ID. Use the show ip protocols, show ip route ospf, show ip ospf interface, show ip ospf, and show ip ospf neighbor commands to verify OSPF operation.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v