How to configure open shortest path first routing protocol

In this article I will demonstrate an example of OSPF Routing configuration. We will use four different series router so you can get familiar with all different platform covered in CCNA exam. Create a topology as shown in figure.

Configuring OSPF is slightly different from configuring RIP. When configuring OSPF, use the following syntax: Router(config)# router ospf process_ID Router(config-router)# network IP_address wildcard_mask area area_# The process_ID is locally significant and is used to differentiate between OSPF processes running on the same router. Your router might be a boundary router between two OSPF autonomous systems, and to differentiate them on your router, you will give them unique process IDs. Note that these numbers do not need to match between different routers so they have nothing to do with autonomous system numbers. To configure any router double click on it and select CLI.To configure this topology use this step by step guide. (1841Router0) Hostname R1 To configure and enable ospf routing on R1 follow these commands exactly. Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#hostname R1 R1(config)#interface fastethernet 0/0 R1(config-if)#ip address 10.0.0.1 255.0.0.0 R1(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up R1(config-if)#exit R1(config)#interface serial 0/0/0 R1(config-if)#ip address 20.0.0.1 255.0.0.0 R1(config-if)#clock rate 64000 R1(config-if)#bandwidth 64 R1(config-if)#no shutdown %LINK-5-CHANGED: Interface Serial0/0/0, changed state to down R1(config-if)#exit %LINK-5-CHANGED: Interface Serial0/0/0, changed state to up R1(config)#router ospf 1 R1(config-router)#network 10.0.0.0 0.255.255.255 area 0 R1(config-router)#network 20.0.0.0 0.255.255.255 area 0 R1(config-router)#exit R1(config)# (2620XM-Router1) Hostname R2 To configure and enable ospf routing on R2 follow these commands exactly. Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#hostname R2 R2(config)#interface serial 0/0 R2(config-if)#ip address 20.0.0.2 255.0.0.0 R2(config-if)#no shutdown %LINK-5-CHANGED: Interface Serial0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up R2(config-if)#exit R2(config)#interface fastethernet 0/0 R2(config-if)#ip address 30.0.0.1 255.0.0.0 R2(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up R2(config-if)#exit %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up R2(config)#router ospf 2 R2(config-router)#network 20.0.0.0 0.255.255.255 area 0 R2(config-router)#network 3 00:03:10: %OSPF-5-ADJCHG: Process 2, Nbr 20.0.0.1 on Serial0/0 from LOADING to FULL, Loading Done0.0.0.0 0.255.255.255 area 0 R2(config-router)#network 30.0.0.0 0.255.255.255 area 0 R2(config-router)#exit R2(config)# (2620XM-Router2)Hostname R3 To configure and enable ospf routing on R3 follow these commands exactly. Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#hostname R3 R3(config)#interface fastethernet 0/0 R3(config-if)#ip address 30.0.0.2 255.0.0.0 R3(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up R3(config-if)#interface serial 0/0 R3(config-if)#ip address 40.0.0.1 255.0.0.0 R3(config-if)#clock rate 64000 R3(config-if)#bandwidth 64 R3(config-if)#no shutdown %LINK-5-CHANGED: Interface Serial0/0, changed state to down R3(config-if)#exit %LINK-5-CHANGED: Interface Serial0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up R3(config)#router ospf 3 R3(config-router)#network 40.0.0.0 0.255.255.255 area 0 R3(config-router)#network 30.0.0.0 0.255.255.255 area 0 00:04:53: %OSPF-5-ADJCHG: Process 3, Nbr 30.0.0.1 on FastEthernet0/0 from LOADING to FULL, Loading D R3(config-router)#exit R3(config)# %SYS-5-CONFIG_I: Configured from console by console R3# (2811Router3) Hostname R4 To configure and enable ospf routing on R4 follow these commands exactly. Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface serial 0/0/0 Router(config-if)#ip address 40.0.0.2 255.0.0.0 Router(config-if)#no shutdown %LINK-5-CHANGED: Interface Serial0/0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to up Router(config-if)#exit Router(config)#interface fastethernet 0/0 Router(config-if)#ip address 50.0.0.1 255.0.0.0 Router(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up Router(config-if)#exit R4(config)#router ospf 4 R4(config-router)#network 50.0.0.0 0.255.255.255 area 0 R4(config-router)#network 40.0.0.0 0.255.255.255 area 0 R4(config-router)# 00:06:32: %OSPF-5-ADJCHG: Process 4, Nbr 40.0.0.1 on Serial0/0/0 from LOADING to FULL, Loading Done R4(config-router)#exit R4(config)# PC-1 PC>ipconfig IP Address......................: 10.0.0.2 Subnet Mask.....................: 255.0.0.0 Default Gateway.................: 10.0.0.1 PC>ping 50.0.0.2 Pinging 50.0.0.2 with 32 bytes of data: Reply from 50.0.0.2: bytes=32 time=156ms TTL=124 Reply from 50.0.0.2: bytes=32 time=127ms TTL=124 Reply from 50.0.0.2: bytes=32 time=156ms TTL=124 Reply from 50.0.0.2: bytes=32 time=140ms TTL=124 Ping statistics for 50.0.0.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 127ms, Maximum = 156ms, Average = 144ms PC> PC-2 PC>ipconfig IP Address......................: 50.0.0.2 Subnet Mask.....................: 255.0.0.0 Default Gateway.................: 50.0.0.1 PC>ping 10.0.0.2 Pinging 10.0.0.2 with 32 bytes of data: Reply from 10.0.0.2: bytes=32 time=140ms TTL=124 Reply from 10.0.0.2: bytes=32 time=141ms TTL=124 Reply from 10.0.0.2: bytes=32 time=157ms TTL=124 Reply from 10.0.0.2: bytes=32 time=156ms TTL=124 Ping statistics for 10.0.0.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 140ms, Maximum = 157ms, Average = 148ms You can verify that ospf is running successfully via show ip protocols command in privilege mode. R4#show ip protocols Routing Protocol is "ospf 4" Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 50.0.0.1 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 50.0.0.0 0.255.255.255 area 0 40.0.0.0 0.255.255.255 area 0 Routing Information Sources: Gateway Distance Last Update 40.0.0.1 110 00:01:26 Distance: (default is 110) R4# You can use show ip oute command to troubleshoot ospf network. If you did not see information about any route checks the router attached with that network. R4#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set O 10.0.0.0/8 [110/1564] via 40.0.0.1, 00:02:37, Serial0/0/0 O 20.0.0.0/8 [110/1563] via 40.0.0.1, 00:02:37, Serial0/0/0 O 30.0.0.0/8 [110/782] via 40.0.0.1, 00:02:37, Serial0/0/0 C 40.0.0.0/8 is directly connected, Serial0/0/0 C 50.0.0.0/8 is directly connected, FastEthernet0/0 R4# To test ospf routing do ping from pc1 to pc2 and vice versa. If you get replay then you have successfully configured ospf routing but if you did not get replay double check this configuration and try to troubleshoot. I have uploaded a configured and tested topology in case you are unable to locate the problem spot then download this configuration file. And try to find out where have you committed mistake ospf routing configurations Configuration command of OSPF Commands Descriptions Router(config)#router ospf 1 Starts OSPF process 1. The process ID is any positive integer value between 1 and 65,535. Router(config-router)#network 172.16.0.0 0.0.255.255 area 0 OSPF advertises interfaces, not networks. Uses the wildcard mask to determine which interfaces to advertise. Router(config-if)#ip ospf hellointerval timer 20 Changes the Hello Interval timer to 20 seconds. Router(config-if)#ip ospf deadinterval 80 Changes the Dead Interval timer to 80 seconds. NOTE: Hello and Dead Interval timers must match for routers to become neighbors Router#show ip protocol Displays parameters for all protocols running on the router Router#show ip route Displays a complete IP routing table Router#show ip ospf Displays basic information about OSPF routing processes Router#show ip ospf interface Displays OSPF info as it relates to all interfaces Router#show ip ospf interface fastethernet 0/0 Displays OSPF information for interface fastethernet 0/0 Router#show ip ospf border-routers Displays border and boundary router information Router#show ip ospf neighbor Lists all OSPF neighbors and their states Router#show ip ospf neighbor detail Displays a detailed list of neighbors Router#clear ip route * Clears entire routing table, forcing it to rebuild Router#clear ip route a.b.c.d Clears specific route to network a.b.c.d Router#clear ip opsf counters Resets OSPF counters Router#clear ip ospf process Resets entire OSPF process, forcing OSPF to re-create neighbors, database, and routing table Router#debug ip ospf events Displays all OSPF events Router#debug ip ospf adjacency Displays various OSPF states and DR/ BDR election between adjacent routers Router#debug ip ospf packets Displays OPSF packets http://computernetworkingnotes.com/routing-static-dynamics-rip-ospf-igrp-eigrp/ospf-routing-configurations.html