OSPF - EIGRP redistribtion question

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May 8th, 2009
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Hi


We're about to implement a new WAN running OSPF which we intend to run alongside our current EIGRP network using route redistribution.


My question is - If a route within the OSPF network goes down, will the L3 switches in the EIGRP network learn about the downed route, and if so how does this process work? Vice versa also.


Any answers much appreciated, as would any issues anyone knows of re OSPF - EIGRP route-redistribution, as this is a first for all of us here!


Regards,

Paul

Correct Answer by Jon Marshall about 8 years 2 months ago

Paul


Redistribution is not a one-off as such. If for example you added a new route to OSPF and as long as you weren't filtering that route in terms of redistribution then yes it would be redistributed into EIGRP.


So it's not a regular update as such, but updates will be made if new routes are added or existing routes are removed.


Jon

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Jon Marshall Fri, 05/08/2009 - 06:33
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Paul


Not entirely sure i understand. If you have an OSPF route that is being redistributed into EIGRP and that route is then removed from OSPF it will stop being redistributed into EIGRP.


As for issues, it sounds like you are going to be doing mutual redistribution. If so if you are redistributing from multiple points in your network you should look at tagging and filtering the routes on the routers performing redistribution.


Jon

PDEdwards Fri, 05/08/2009 - 06:41
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Jon,


Thanks for your reply.

Not having done any route-redistributing before I was unsure how one protocol would inform another of a downed route. I suppose I was thinking of the route-redistribution process as a 'one-off'. I.e EIGRP learns about all the routes in the OSPF network in one hit. Then if one of these OSPF routes goes down I wasn't sure of the mechanism by which EIGRP learns about this.


Are you saying that the route-redistribution is a dynamic process - i.e OSPF informs EIGRP at regular intervals of the routes it knows, and if one of these goes down it will be missing from the update and will therefore be removed from the EIGRP process?


It's the mechanics I'm unsure off!


Kind Regards,

Paul

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Jon Marshall Fri, 05/08/2009 - 06:55
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Paul


Redistribution is not a one-off as such. If for example you added a new route to OSPF and as long as you weren't filtering that route in terms of redistribution then yes it would be redistributed into EIGRP.


So it's not a regular update as such, but updates will be made if new routes are added or existing routes are removed.


Jon

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