Route Redistribution

There may be instances where you’ll encounter networks running multiple routing protocols.   Route redistribution allows one or more routers to take the routes they’ve learned through their own protocol and share those prefix’s with other routing protocols.

Here is the syntax of the redistribute command:

redistribute protocol [ process-id ] [ level-1 | level-1-2 | level-2 ] [ as-number ] [ metric metric-value ] [ metric-type type-value ] [ match { internal | external 1 | external 2 }] [ tag tag-value ] [ route-map map-tag ] [ subnets ]

The command defines the routing source from which routes are taken and also defines the process into which those routes will be advertised.

Certain routing protocols require a metric to be set in order to be redistributed, like EIGRP, and RIP.  OSPF will automatically apply its external type metric by default, but you can define what kind of external route type is used.

You can apply a specific tag to the redistributed routes, which is useful for filtering across multiple network redistribution points to prevent routing loops or unintended places for routes to be injected.

You can also apply a route map to the redistribute command, that can match routes to be advertised and filter any you don’t want advertised.

 

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