ARP Suppression - VxLAN

[Vivek Ganapathi]

Hi all,

Trying to understand the requirement of ARP suppression in VxLAN implementations using BGP EVPN. Why do we really need ARP suppression turned on when BGP based implementation does ARP optimization in first place? Basically, ARP suppression is just about building a cache table to advise an end host the MAC address of the remote VTEP it was sending the ARP request to. Basically there is no broadcast on the fabric as the ARPs are sent as Multicast instead of Broadcast.

So the question is what ARP suppression does effectively?

Regards

Vivek

[shulipal]

Hi Ganapathi,

ARP flooding can occur for the initial ARP request to a silent host in the network. The VTEPs in the network don’t see any traffic from the silent host until another host sends an ARP request for its IP address, and an ARP response is sent back. After the local VTEP learns about the MAC and IP addresses of the silent host, the information is distributed through the MP-BGP EVPN control plane to all other VTEPs. Any subsequent ARP requests do not need to be flooded.

Most end hosts send GARP or RARP requests to announce themselves to the network immediately after they come online, the local VTEP immediately has the opportunity to learn their MAC and IP addresses and distribute this information to other VTEPs through the MP-BGP EVPN control plane. Therefore, most active IP hosts in VXLAN EVPN should be learned by the VTEPs either through local learning or control-plane-based remote learning. As a result, ARP suppression reduces the network flooding caused by host ARP learning behavior.

Thanks,

Shivakumar Hulipalled