Implementing OSPF Single Area OSPF Implementation 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 1 OSPF Overview Creates a neighbor relationship by exchanging hello packets Propagates LSAs rather than routing table updates Link Router interface State Description of an interface and its relationship to neighboring routers routers Floods LSAs to all OSPF routers in the area not just directly connected Pieces together all the LSAs generated by the OSPF routers to create the OSPF link state database Uses the SPF algorithm to calculate the shortest path to each destination and places it in the routing table 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 2 OSPF Hierarchy Example Minimizes routing table entries Localizes the impact of a topology change within an area 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 3 Neighbor Adjacencies The Hello Packet 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 4 SPF Algorithm 10 10 1 1 1 Places each router at the root of a tree and calculates the shortest path to each destination based on the cumulative cost Cost Reference Bandwidth Interface Bandwidth b s 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 5 Configuring Single Area OSPF RouterX config router ospf process id Defines OSPF as the IP routing protocol RouterX config router network address wildcard mask area area id Assigns networks to a specific OSPF area 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 6 Configuring Loopback Interfaces Router ID Number by which the router is known to OSPF Default The highest IP address on an active interface at the moment of Can be overridden by a loopback interface Highest IP address of any active OSPF process startup loopback interface Can be set manually using the router id command 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 7 Verifying the OSPF Configuration RouterX show ip protocols Verifies that OSPF is configured RouterX show ip route Displays all the routes learned by the router RouterX show ip route Codes I IGRP derived R RIP derived O OSPF derived C connected S static E EGP derived B BGP derived E2 OSPF external type 2 route N1 OSPF NSSA external type 1 route N2 OSPF NSSA external type 2 route Gateway of last resort is 10 119 254 240 to network 10 140 0 0 O 10 110 0 0 110 5 via 10 119 254 6 0 01 00 Ethernet2 O IA 10 67 10 0 110 10 via 10 119 254 244 0 02 22 Ethernet2 O 10 68 132 0 110 5 via 10 119 254 6 0 00 59 Ethernet2 O 10 130 0 0 110 5 via 10 119 254 6 0 00 59 Ethernet2 O E2 10 128 0 0 170 10 via 10 119 254 244 0 02 22 Ethernet2 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 8 Verifying the OSPF Configuration Cont RouterX show ip ospf Displays the OSPF router ID timers and statistics RouterX show ip ospf Routing Process ospf 50 with ID 10 64 0 2 output omitted Number of areas in this router is 1 1 normal 0 stub 0 nssa Number of areas transit capable is 0 External flood list length 0 Area BACKBONE 0 Area BACKBONE 0 Area has no authentication SPF algorithm last executed 00 01 25 028 ago SPF algorithm executed 7 times output omitted 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 9 Verifying the OSPF Configuration Cont RouterX show ip ospf interface Displays the area ID and adjacency information RouterX show ip ospf interface ethernet 0 Ethernet 0 is up line protocol is up Internet Address 192 168 254 202 Mask 255 255 255 0 Area 0 0 0 0 AS 201 Router ID 192 168 99 1 Network Type BROADCAST Cost 10 Transmit Delay is 1 sec State OTHER Priority 1 Designated Router id 192 168 254 10 Interface address 192 168 254 10 Backup Designated router id 192 168 254 28 Interface addr 192 168 254 28 Timer intervals configured Hello 10 Dead 60 Wait 40 Retransmit 5 Hello due in 0 00 05 Neighbor Count is 8 Adjacent neighbor count is 2 Adjacent with neighbor 192 168 254 28 Backup Designated Router Adjacent with neighbor 192 168 254 10 Designated Router 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 10 Verifying the OSPF Configuration Cont RouterX show ip ospf neighbor Displays the OSPF neighbor information on a per interface basis RouterX show ip ospf neighbor Pri State Dead Time Address Interface ID 10 199 199 137 1 FULL DR 0 00 31 192 168 80 37 FastEthernet0 0 1 FULL DROTHER 0 00 33 172 16 48 1 FastEthernet0 1 172 16 48 1 172 16 48 200 1 FULL DROTHER 0 00 33 172 16 48 200 FastEthernet0 1 10 199 199 137 5 FULL DR 0 00 33 172 16 48 189 FastEthernet0 1 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 11 Verifying the OSPF Configuration Cont RouterX show ip ospf neighbor 10 199 199 137 Neighbor 10 199 199 137 interface address 192 168 80 37 In the area 0 0 0 0 via interface Ethernet0 Neighbor priority is 1 State is FULL Options 2 Dead timer due in 0 00 32 Link State retransmission due in 0 00 04 Neighbor 10 199 199 137 interface address 172 16 48 189 In the area 0 0 0 0 via interface Fddi0 Neighbor priority is 5 State is FULL Options 2 Dead timer due in 0 00 32 Link State retransmission due in 0 00 03 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 12 OSPF debug Commands RouterX debug ip ospf events OSPF hello with invalid timers on interface Ethernet0 hello interval received 10 configured 10 net mask received 255 255 255 0 configured 255 255 255 0 dead interval received 40 configured 30 OSPF rcv v 2 t 1 l 48 rid 200 0 0 117 aid 0 0 0 0 chk 6AB2 aut 0 auk RouterX debug ip ospf packet OSPF rcv v 2 t 1 l 48 rid 200 0 0 116 aid 0 0 0 0 chk 0 aut 2 keyid 1 seq 0x0 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 13 Load Balancing with OSPF OSPF load balancing Paths must be equal cost By default up to four equal cost paths can be placed into the routing table With a configuration change up to a maximum of 16 paths can be configured config router maximum paths value To ensure paths are equal cost for load balancing you can change the cost of a particular link config if ip ospf cost value 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 14 Load Balancing with OSPF 2007 Cisco Systems Inc All rights reserved ICND2 v1 0 4 15 OSPF Authentication OSPF supports two types of authentication Plaintext or simple password authentication MD5 authentication The router generates and checks every OSPF packet The router authenticates …