Friday, April 24, 2020

Cisco EVPN HMM Different MAC address

Hey all, this is a bit of an in-depth question regarding Cisco EVPN Fabric, HMM, and Multisite. Please bear with me while I try to detail the scenario.

So, within my EVPN fabric HMM works just fine, the VM pops up on a new VTEP the old MAC route is removed and the new one is added and traffic flows just fine. I'm having a problem regarding a VIP attached to 2 different hosts, HostA and HostB. HostA is in DC1 and HostB is in DC2.

HostA has an IP of 10.1.1.101 a MAC of 0000.1111.2222, HostB has an IP of 10.1.1.102 a MAC of 0000.2222.3333. The VIP is 10.1.1.100. When the VIP moves between hosts the l2vpn route gets added, but the old one stays in the BGP table. This makes sense since it's a different MAC address, but because of this the traffic to that VIP gets blackholed in the site that no longer has that VIP. That site still thinks that the route is local, and will continue to think that until it's finally removed from the BGP route table. I think that happens when the ARP entry times out on the old VTEP, but I'm not certain.

I've been googling around to find any details on this type of situation but have been unsuccessful. Has anyone else dealt with this, and possibly shed some light on how this should be handled?

Thanks!



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