Cisco CCNA:Configure and Enable OSPF (OSPF-related knowledge points III)

Configuring OSPF Configuring basic OSPF isn’t as simple as RIP,IGRP, and EIGRP, and it can get really complex once the many options that are allowed within OSPF are factored in. But that’s OK- for your studies, you should be interested in the basic single area OSPF configuration. The following sections describe how to configure single area OSPF.

These two elements are the basic elements of OSPF configuration:

Enabling OSPF Configuring OSPF areas

Enabling OSPF The easiest and also least scalable way to configure OSPF is to just use a single area. Doing this requires a minimus of two commands. The command you use to activate the OSPFrouting process is: Lab-A(config)#router ospf? <1-65535> A value in the range 1-65535 identifies the OSPF Process ID. It’s a unique number on this router that groups a series of OSPF configurations commands under a specific running process. Different OSPF routers don’t have to use the same Process ID in order to communicate. It’s purely a local value that essentially has little meaning, but it cannot start at 0, it has to start at a minimum of 1. You can have more than one OSPF process running simultaneously on the same router if you want, but this isn’t the same as running multi-area OSPF. The second process will maintain an entirely separate copy of its topology table and manage its communications independently of the first process. Note: The OSPF Process ID is needed to identify a unique instance of an OSPF database and is locally significant. Configuring OSPF Areas After identifying the OSPF process, you need to identify the interfaces that you want to activate OSPF communications on, as well as the area in which each resides. This will also configure the networks you are going to advertise to others. OSPF uses wildcards in the configuration- which are also used in access list configurations. Here is an OSPF basic configuration example for you: Lab-A#config t Lab-A(config)# router ospf 1 Lab-A(config-router)# network 10.0.0.0.0.255.255.255 area? <0-4294967295> OSPF area ID as a decimal value A.B.C.D OSPF area ID in IP address format Lab-A(config-router)# network 10.0.0.0.0.255.255.255 area 0 Note: The areas can be any number from 0 to 4.2 billion. Don’t get these numbers confused with the Process ID, which is from 1 to 65535. Remember, the OSPF Process ID number is irrelevant. It can be the same on every router on the network, or it can be different-doesn’t matter. It’s locally significant and just enables the OSPF routing on the router. The arguments of the network command are the network number(10.0.0.0) and the wildcard mask(0.255.255.255). The combination of these two numbers identifies the interfaces that OSPF will operate on, and will also be included in its OSPF LSA advertisements. OSPF will use this command to find any interface on the router configured in the 10.0.0.0 network, and it will place any interface it finds into area 0. Notice that you can create about 4.2 billion areas.(I doubt that a router would let you actually create that many, but you can certainly name them using the numbers up to 4.2 million.) You can also lable an area using an IP address format. Verifying OSPF Configuration The show ip ospf command can display OSPF information for one or all OSPF processed running on the router. Information contained therein includes the Router ID, area information, SPF statistics, and LSA timer information. The show ip ospf database command indicates the number of links and the neighboring router’s ID and the topology database. The show ip ospf interface command will show all interface-related OSPF information including: Interface IP address,Area assignment,Process ID,Router ID,Network type,Cost,Priority,DR/BDR election informatin(if applicable),Hello and Dead timer intervals,Adjacent neighbor information The show ip ospf neighbor command can summarize the pertinent OSPF information regarding neighbors and the adjacency state. If a DR or BDR exists, that information will also be displayed. The show ip protocols command will provide an excellent overview of the actual operation of all currently running protocols.

Flickr : 640-802, 640-822, Configure and Enable OSPF, ccna, cisco, cisco certification, ospf, routing protocol

Popularity: 3% [?]