VXLAN vPC behaviour (CML)

[19RedWolf81]

Hi All,

I'm getting some odd behaviour in my VXLAN Lab within CML. This only happens when I enable the vPC feature on the LEAF switch (no other vPC configuration has been applied, only the feature has been enabled). 

• Client3 on the LEAF switch with the vPC feature enabled can't resolve any other clients on another LEAF switch.
• Client1 which is on a standalone LEAF switch can resolve Client3 and successfully ping Client3.
• Now Client1 has pinged Client3, Client3 can now ping Client1.

This seems to be a problem with BUM traffic from the LEAF switch not being forwarded when the vPC feature is enabled. If I disable the vPC feature the behaviour stops and the switch forwards the BUM traffic normally.

The Nexus Image Version: 10.5.1.F, CML 2.8.1

Has anybody else come across this behaviour at all.

Many Thanks

Scott

[M02@rt37]

Hello @19RedWolf81 

Interesting point.

If you go further with vPC config (vpc domain), you have the same symptom ?

With vpc feature enabled, EVPN may suppress or modify BUM handling, especially if peer-gateway is expected but not configured.

[balaji.bandi]

When I was testing VXLAN, I used vPC between Leaf switches, and it worked as expected (as  I remember, and let me check my notes).

As i see this may be virtual environment issue, what is the reason of enabling vpc feature if not used ?

[19RedWolf81]

M02@rt37 Yes, I get the same behaviour with full vPC configuration in place. I think this is an issue in the 10.5.1 NX-OS image as I have seen several labs on the internet using VXLAN with vPC but using older NX-OS images. I might try importing an older image into CML and giving it another go.

@balaji.bandi I'm building labs to get a better understanding of VXLAN concepts/design and troubleshooting. I find reading information can only take you so far, I find nothing better than getting on CLI and configuring it.

[19RedWolf81 · Accepted solution]

Well after importing the following NX-OS image 10.3.5.M into CML. My lab is now working as expected.

Note: I have also found that using a second loopback interface for the NVE interface anycast address, does not work in CML.

[M02@rt37]

Thanks a lot for you feedback @19RedWolf81