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Cisco Mutual redistribution between EIGRP and BGP and match statements

Posted on 2016-08-31
Medium Priority
Last Modified: 2016-09-06
Hello Experts

I'm working on a mutual redistribution problem between EIGRP and BGP

The idea is set a tag (210) to traffic coming from our LAN on R2-2 so that it can be matched and denied on R3-7. The goal is to prevent routing loops.

The routes are being redistributed into R1-1, but I'm not able to see if the routes are being tagged.

Can someone let me know how to verify routes are being filtered with the route-maps?

TBH, I don't think its working at all.

I have attached the configs and show commands.

I read somewhere the problem was with command match route-type internal, but I'm not sure if that is the problem

Any help will be greatly appreciated.

Question by:Member_2_7966113
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LVL 31

Expert Comment

ID: 41778199
Once again (I wrote the same for OSPF redistribution).
You can't tag routes while you redistribute routes into BGP (at least not with route map set tag <number>).

You can check route tag typically by using
# sh ip route x.x.x.x    <--- specific route that you need to check (easy on router on what you are not doing redistribution)
# sh ip eigrp topology  <--- for routes imported into EIGRP
# sh ip ospf database   <--- for routes imported into OSPF
LVL 31

Expert Comment

ID: 41778439
You can find article about BGP autotagging here.
I remembered that scenario when I saw message
% "TAG" used as redistribute ospf into bgp route-map, set tag not supported
Did not go deep in configurations from your links currently, but as much as I can see it is the same what I already wrote you for ospf to bgp mutual redistribution. There is no tagging OSFP while redistributing in BGP (but did not go too deep into configs 2- 4, I just checked the first one).
One of your possible solutions is to change AD of BGP to look worse than EIGRP or OSPF (on edge routers) so as long as internal routes exist internal routes with lower AD will be placed in routing table of edge routers. Changing AD for routing protocols is locally significant, so it will not affect any other routers.
But scenario should be real life, otherwise I am not sure which loop prevention mechanism to apply since there is more than one option for those scenarios.
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Author Comment

ID: 41778492
Hi Predrag,

Thanks again for responding. You have been very helpful.

Because I was certain it worked I also posted the question on Cisco website. This is what they have to say:
LVL 31

Accepted Solution

Predrag earned 2000 total points
ID: 41778560
However, how can I verify traffic that routing loops will be prevented? Basically, I shouldn't be able to see network in R5-8 and I shouldn't be able to see in R3-3
Non edge router will always prefer non external routes in the case of OSPF or EGRP. OSPF when redistribute from other protocols marks routes as E1 or E2 type. EIGRP for external routes have AD 170 internal AD 90. However for edge routers, by default, BGP routes are more attractive (better AD), so changing administrative distance for BGP on edge routers from 20 to 180 can also solve some potential problems, or create some new :) (redundant routes received over BGP will not be placed in routing table of edge routers), but again, it all depends on full scenario what you want to achieve.
I read somewhere the problem was with command match route-type internal, but I'm not sure if that is the problem
In your scenario match route-type internal is equal to tagging of routes while redistributing to OSPF and filtering on redistribution to BGP).

Author Comment

ID: 41778806
Hi Predrag,

Thanks again for your input.

I'm not sure what your conclusion is?
LVL 31

Expert Comment

ID: 41779224
No conclusion, just suggestions to what you should pay attention too.
Redistribution and loop prevention can be done in several ways and the best way (easiest way) may be protocol or scenario specific.

Author Closing Comment

ID: 41785936
Hi Predrag, if think we have both come to the same conclusion. In any case your answers pointed me in the right direction

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