05-12-2022 04:35 AM
Hi guys,
thanks for a great resource!
I'm looking at this document on the topic:
Cisco IOS-XR BGP with MPLS Designs
It says in section 4 that in order to make the exchange (In image 3) work ASBR3 needs to have a dummy iBGP neighbor configured. The doc just says there in this instance is an issue with advertising the vpnv4 routes from ASBR3. It doesn't really explain why.
I realize that this is a corner case, since irl more routers would exist within the average AS.
I'm hoping someone can elaborate.
Appreciated, thanks.
Cheers
Solved! Go to Solution.
05-12-2022 10:31 AM - edited 05-12-2022 11:01 AM
Hi @kim ,
I ran the test with XRv 6.3.1 and it works like a charm.
Regards,
05-12-2022 07:15 AM
Hi @kim
I am not sure what the restriction was, but this restriction is not present in recent XR versions. I just ran a quick test and it worked like a charm without the dummy ibgp session on the middle ASBR.
Regards,
05-12-2022 10:19 AM
Hi @Harold Ritter,
thanks!
Well thats interesting, that an iBGP peer is needed to trick XR into passing eBGP routes - which version did you test on? Feels kind of like a bug i ran into once where the XE didn't populate forwarding tables if CDP wasnt turned on for a specific interface. I'll compare to my lab, just needed to reach a milestone in the workbook.
Cheers!
05-12-2022 10:31 AM - edited 05-12-2022 11:01 AM
Hi @kim ,
I ran the test with XRv 6.3.1 and it works like a charm.
Regards,
05-12-2022 11:37 AM
Hey
Wow, okay - i'm running 6.5.3, promising - well now i cant wait to test it. The doc was updated june last year...
Thanks again!
Cheers
05-12-2022 11:52 AM
Hi @kim ,
Let us know if you run into issues or questions while testing.
Regards,
05-12-2022 01:48 PM
Hey
Ok tested it, works perfectly here as well. Go figure. Wonder what section 4 was originally about.
Anyway, thanks guys
Cheers
05-12-2022 12:56 PM - edited 05-12-2022 01:16 PM
I know this issue solved but I want to mention something here
If I am right this B2B inter-AS "option-B" so
there is two way the AS exchange label
1- config the LDP under the interface connect both AS
2- config the BGP to exchange label <- are this what is ask for??
05-12-2022 01:01 PM
Hey
Well even though it was solved, any input is appreciated!
This is option b though, Option B
Option a is more like how you would build your bgp towards the end customer, just with the added label path maybe.
Cheers
05-12-2022 01:27 PM
OK let me review my note within two days I will inform you what I get
""why we use dummy iBGP with Inter-AS op.B IOS XR ?""
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