Migrate BGP border router: c7600 IOS to ASR9K

[leon.mflai]

Hi,

Doing a migration. During comparison of "show bgp nei x.x.x.x advertised-routes" between existing C7600 vs new ASR9K. Found that there were some r>i (RIB-Failure) route in C7600 doesn't flagged w/ r>i in ASR9K.

Is it normal behaviour in ASR9K?

How can I perserve r>i on ASR9K? Due to my IGP (e.g. AD etc) issue or ASR9K IOS-XR hidden config / default config issue?

Need help urgently! and hope Cisco ppl can help.

Leon

[Peter Paluch]

Hello Leon,

The first question you should answer yourself is why there are r-flagged routes on your 7600 router - what is the exact reason BGP was unable to install these routes into the RIB. The show ip bgp rib-failure command may provide additional information about the cause of the RIB failure. Also see the following document:

http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a00800949e8.shtml#twenty-three

Now, after you have precisely identified the cause of these RIB failures, verify whether the same conditions exist on your ASR. Obviously, if there is no reason that prevents BGP from installing all routes into the RIB, such as routes of a lower administrative distance already being present in RIB, you will not see any RIB failures because there is no reason for them to occur.

I understand that I am basically answering by posing counterquestions but the answer really lies by you.

Please keep us informed!

Best regards,

Peter

[leon.mflai]

Hi,

Tks for speedy reply.

Checked exisitng C7600 that reason is "Higher admin distance".

Is there way to verify in ASR9k?

[Peter Paluch]

Hello Leon,

What kind of IOS-XR are you running on the ASR9K?

Is there way to verify in ASR9k?

Well, take a simple BGP route that gets RIB-failed on the 7600. Then check what kind of route has been installed into the RIB instead and why. After that, check whether the same route is present on the ASR9K and if it is missing, verify why is it missing. Please understand that at this level of knowledge, I can not be more specific: if the route is a static route that it most probably has not been configured on the ASR. If the route is learned from IGP then the question is why it has not been learned via IGP on the ASR.

By the way, when looking into the command reference, it indeed seems that there is no RIB-Failure flag present on the IOS-XR. It may be we are hunting a non-existent issue. I recommend checking whether the routing table on the ASR is correct and sensible. All that counts, anyway, is the routing table and its contents.

Best regards,

Peter

[leon.mflai]

Hi,

ASR9K w/ IOS-XR 4.2.3. RSP440 + Typhoon Mod80 LC.

[Peter Paluch]

Hi Leon,

Is the missing of RIB Failure the only indication you're finding to be a problem? Is the routing table on the ASR otherwise correct? It may be that we are trying to solve a cosmetical problem here. I have browsed through the IOS-XR documentation and I have found no mention of RIB-Failure. It is simply possible that IOS-XR does not specifically call the conflicts between BGP-learned routes and other routes present in RIB as RIB-Failures.

Best regards,
Peter