Handling Asymmetry with OMP Preference

[dodgerfan78]

I have the following scenarion:

• A site with 2 vEdges: vEdge1 and vEdge2 each with their own ISP connection.
• Each vEdge has a TLOC extension to other in case their ISP goes down.
• Each vEdge also has ZBFW enabled so traffic must be kept symmetric.
• On the LAN side, we have VRRP with vEdge1 as primary
• We have a hub and spoke topology where the Hub currently chooses all routes from vedge1.
• When vEdge1 ISP goes down, the TLOC extension takes over and OMP path is still good. However, the Hub now chooses the site routes via vEdge2 which break the symmetric path and traffic is dropped.

Why does the Hub choose vedge2 even though vedge1 is still valid via the TLOC extension? Is there something that can be done to make the Hub prefer vEdge1?

[MHM Cisco World]

do you use color strict ?

MHM

[dodgerfan78]

No. When i turn off the Zone based policy, traffic works. I tried using affinity groups which then forced the hub to use vedge1 as next hop but traffic was still getting dropped when the policy was enabled. I just configured a VRRP tracker which now made vedge2 primary. This works but i was wondering if there was a better way. The whole point of TLOC extension is this vedge1 still can route. Maybe when you have these stateful configurations like ZBFW, tloc extension isn’t good.

[MHM Cisco World]

Can you share topolgy 

Thanks alot

MHM

[Kanan Huseynli]

Hi,

which version do you use? Is it vedge or cedge (ios xe)? The problem is most likely due to routing. You need to check omp route result for LAN subnets of VRRP site to understand to which it is failovered when ISP1 is down.