Route maps and redistribution

[NetMonkey]

Not sure why my original post didn't show.

My question is why, when and how would we apply route maps to redistribution.

I get that when you redistribute between two routing protocols such as OSPF and EIGRP we need to adjust the default metrics but not sure how the route map comes into this? If we set the metric manually why would a route map be needed? 

Thanks

[paul driver]

@NetMonkey 

And the question is?

[balaji.bandi]

Not sure what you referring to here, maybe give some examples, what you looking todo by setting metric, not route-map not use case for you.

Sometimes we use different use cases to meet different requirements it all depends on what you want to achieve the end goal.

some reference :

https://community.cisco.com/t5/networking-documents/route-redistribution-filtering/ta-p/3152812

[Richard Burts]

The original post asks very open ended questions about using route maps with redistribution: why use a route map with redistribution, when to use a route map with redistribution, and how to use a route map with redistribution. Here are my explanations of the 3 questions:

1) why use a route map with redistribution. If you redistribute from one routing protocol to another routing protocol by default all routes learned in the originating protocol are sent to the receiving protocol. If that is the desired outcome then there is no need for a route map. But sometimes we want to exert some control over what is redistributed so that only some of the routes from the originating protocol are sent to the receiving protocol. Route Map is one way to exert that control. (distribute list is another way to exert that control).

2) when to use a route map with redistribution. This is closely related to 1). If you are doing redistribution and you want to exert control over what routes are redistributed then you would use a route map.

3) how to use a route map. Within a route map there may be one or multiple statements. Within each statement there might be zero or one or more match clauses which can identify certain routes and can permit or deny those routes to be distributed. Within each statement there might be zero or one or more set clauses which can establish values assigned to the redistributed route (especially to set the metric of the redistributed route).

Route maps can be a complicated topic to explain. I hope this simple explanation is enough to satisfy this open ended question.

[paul driver]

Hello
You can be more deterministic with route-maps, as you can match on a alot of variables such as access/prefix list, metrics, source ip/protocol etc..
So an example would be you are performing mutual redistribution and you wish to advertised partial routes with a certain metrics between the two routing processes that relate to an access/prefix list and any thing thats not subject to that access/prefix list would not be advertised or would not set a metric.

In the same scenario if you had dual redistribution points performing mutual redistribution you could negate network loops by tagging the original redistribute routes within route-maps so those same routes don’t get re-advertised back into their original routing process