Border node route issue

techno.it — Thu, 09 Dec 2021 22:07:27 GMT

Hello,

I'm having trouble wrapping my head around a weird issue. I have two borders and one single fusion switch and they only have B1F1 and B2F1 connections. I have imported a route on the Fusion router so that I can leak into the fabric but the border node giving surprising results upon checking the routing table, FB1 learning routes via LISP instead of BGP, and CEF entry display the next-hop using the LISP tunnel!!

As an end result, the host inside the fabric cannot reach this subnet located outside the fabric.

I have checked border nodes have no static routes configured for this route.

Appreciate any suggestions

Here are some output;

FB1#sh ip route vrf PROD | in 10.1.20.28/30
l 10.1.20.28/30 [250/1], 2d01h, Null0

FB1#sh ip cef vrf PROD | in 10.1.20.28
10.1.20.28/30 10.1.25.10 LISP0.4099

FB1#sh ip bgp vpnv4 vrf PROD

*> 10.1.20.28/30 0.0.0.0 10 32768 ?

FB1#sh ip lisp map-cache detail eid-table vrf PROD

10.1.20.28/30, uptime: 2d01h, expires: 22:16:44, via map-reply, complete
Sources: map-reply, site-registration
State: complete, last modified: 2d01h, map-source: 10.1.25.10
Exempt, Packets out: 17924(10063175 bytes) (~ 00:00:03 ago)
Configured as EID address space
Locator Uptime State Pri/Wgt Encap-IID
10.1.25.10 2d01h up 10/10 -
Last up-down state change: 2d01h, state change count: 1
Last route reachability change: 2w6d, state change count: 11
Last priority / weight change: never/never
RLOC-probing loc-status algorithm:
Last RLOC-probe sent: never

Re: Border node route issue

Jonathan Cuthbert — Fri, 17 Dec 2021 21:56:44 GMT

Do you have a diagram you could share along with the type of border nodes you are using (external or anywhere)?

Re: Border node route issue

markus.forrer — Sat, 18 Dec 2021 09:28:49 GMT

Maybe have a look at https://www.cisco.com/c/en/us/support/docs/cloud-systems-management/dna-center/213525-sda-steps-to-configure-fusion-router.html#anc12
Inside the section of Fusion VRF Leaking.
BGP allowas-in and route filtering is needed

Re: Border node route issue

techno.it — Sat, 18 Dec 2021 12:26:14 GMT

Issue has been resolved. There was no community tags configured thus causing the LISP and BGP redistribution loop.

@markus.forrer

Thanks for sharing the link

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