External Routes

In OSPF, external routes are classified either as Type E1 or Type E2; the difference is the calculation of the metric (cost) associated with each route. Specifically, a Type E2 route has a metric that is equal to the external cost, whereas a Type E1 route has a metric of the external cost plus the internal cost to that route. Remember the following points when performing redistribution:

• By default, all redistributed routes are automatically categorized as Type E2 by OSPF.

• You can alter the type of external routes during redistribution if you want.

You can select the type of external route that you want the new routes to be through the use of the metric-type keyword when using the redistribute command, as follows:

Trinity(config)#router OSPF 100

Trinity(config-router)#redistribute rip metric-type ?

1 Set OSPF External Type 1 metrics

2 Set OSPF External Type 2 metrics Trinity(config-router)#

The next section discusses the use of default routes in OSPF and as part of redistribution.

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