Hello everyone,
When comparing EVPN to Flood and Learn, one of the most significant improvements is control plane learning. It's implied that when EVPN is used, MAC addresses are advertised via BGP, but in reality, hosts still need to ARP for MAC addresses when initially trying to start communicating with other hosts in the same L2 domain. What is the use of EVPN if we're talking about type 2 routes only and if we do not use ARP suppression? We still need to ARP, and VTEPs would still replicate the ARP and send it to all other VTEPs, thus learning still occurs in the data plane.
So why is EVPN posed as some sort of improvement and fancy control plane learning when in reality MAC/MAC-IP advertisement is not eliminating the necessity of data plane learning for hosts across VXLAN fabric?
I have tested this in the CML and on production equipment, and every time the host needs to communicate with another host in the same L2 domain, it would send an ARP (obviously), and the VTEP would replicate the BUM to all other VTEPs, and then ARP Reply would take the same path. This is no different from flood and learn or even static replication.
I hope someone could provide me with some clarity on the matter. Thank you in advance.
