May 29, 2010

OSPF Basic Config

Easy Pinpoint OSPF configurations on Cisco Routers
OSPF, as we all know is one of the most widely used IGPs today. Having knowledge of OSPF configurations is very important for any Network Engineer. Below are the steps given for OSPF configuration in your network.
NOTE:  Bofore starting OSPF configuration on your Router, you must have at least 1 "UP" and active interface.
A major part of OSPF routing configuration in Cisco IOS is specifying the interfaces on which you want to run OSPF and the OSPF areas to which these interfaces belong. IOS gives you two configuration mechanisms:
  1. 1. The first mechanism is using "network" command within in the OSPF routing process configuration. The "network" command allows you to specify an ACL-like filter that can match multiple interfaces with a single command, significantly reducing the configuration complexity.
              Router # configure terminal
              Router(config) # router ospf [process-id]
        Router(config-router) #network [ip-address] [wildcard-mask] area [area]
 EXAMPLE:
        Router # configure terminal
              Router(config) # router ospf 555
        Router(config-router) #network 10.0.0.0 0.255.255.255 area 0
2. The easiest, but less known method of configuring OSPF is via using interface-mode command for enabling OSPF. Syntax for using this command is explained below:
        Router # configure terminal
        Router(config) # interface [interface-type]  [interface-number]
        Router(config-if) # ip ospf [process-id] area [area-id]
 EXAMPLE:
        Router # configure terminal
        Router(config) # interface serial 1/0
        Router(config-if) # ip ospf 555 area 0
Both methods would accomplish exactly same task, i.e enabling OSPF on Serial 1/0 with OSPF process-id 555 (before using "network" command, you must have the ip address configured on Serial 1/0 within 10.0.0.0 network range).
Other useful OSPF commands are explained in next post. Hope it helped.

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