Section 5.5: Router Configuration

5.5.1: Configuring OSPF

There are a few simple commands that are used to configure and troubleshoot a Cisco router configured to use OSPF in a single area and in a multiple area network. The commands used to configure OSPF are:

router ospf < process_number > where process_number is a number local to the router. This command configures OSPF as the routing protocol on the router.
network network_number wildcard_mask defines the networks that are to participate in the OSPF updates and the area that they reside in.
interface loopback < interface_number > ip address < ip_address > < subnet_mask > defines a loopback interface, which is a virtual interface, on the router.
ip ospf cost < cost > sets the default cost for the router.
auto-cost reference-bandwidth changes the OSPF cost formula.

Note: The ip ospf cost command overrides the auto-cost reference-bandwidth command.

5.5.2: Verifying the OSPF Configuration

There are a number of show ip commands that can be used when troubleshooting an OSPF network. These commands are:

show ip ospf, which provides information about the OSPF process and its details.
show ip ospf database, which provides information about the contents of the topological database.
show ip ospf interface, which provides information on how OSPF has been configured on each interface.
show ip ospf neighbor, which displays all the information about the relationship that the router has with its neighbors.
show ip protocols, which displays the IP configuration on the router, including the interfaces and the configuration of the IP routing protocols.
show ip route [ip-address [mask] [longer-prefixes]] | [protocol [process-id]], which provides detailed information on the networks that the router is aware of and the preferred paths to those networks. It also gives the next logical hop as the next step in the path.
debug ip ospf events, which issues log messages for each OSPF packet.
debug ip ospf packet, which issues log messages describing the contents of all OSPF packets.

5.5.3: Configuring EIGRP

The commands used to configure EIGRP on a Cisco router are consistent with the other IP routing protocol commands. The EIGRP commands are:

router eigrp autonomous_system_number configures EIGRP as the routing protocol on the router.
network network_number [ wildcard_mask ] defines the networks that are to participate in the EIGRP updates. The [ wildcard_mask ] optional parameter identifies which interfaces are running EIGRP.
no network network_number [ wildcard_mask ] disables EIGRP.
no autosummary turns off automatic summarization.
ip summary address eigrp autonomous_system_number ip_address subnet_mask configures summarization at the interface level.
variance multiplier configures EIGRP to load-balance across unequal paths.
bandwidth line_speed overrides the default bandwidth settings on the links.

5.5.4: Verifying the EIGRP Configuration

There are a number of show and debug commands that can be used to configure, maintain, and troubleshoot a live EIGP network. The show commands are:

show ip eigrp neighbors, which provides detailed information on the neighbors.
show ip eigrp topology, which provides details about the routes held in the topology table and for detailed information on the networks that the router is aware of and the preferred paths to those networks, as well as the next logical hop as the first step in the path.
show ip eigrp topology all, which provides details about all the routes and alternative paths held in the topology table.
show ip eigrp traffic, which provides information on the aggregate traffic sent to and from the EIGRP process.
show ipx route, which shows the routing table for IPX and is the source of the information on how to reach the remote destination network.
show ip route, which provides detailed information on the networks that the router is aware of and the preferred paths to those networks.
show ip protocols, which displays the IP configuration on the router, including the interfaces and the configuration of the IP routing protocols.