Tag :: BUM

Disabling the flooding of broadcast, multicast, and unknown unicast traffic into the VXLAN fabric can significantly reduce bandwidth consumption in the VXLAN underlay. This is particularly beneficial in use cases where such traffic is unnecessary. This feature, exclusively supported with EVPN, allows for the selective flooding of ARP and/or ND traffic, offering further control over bandwidth usage.

By default, when an SVI is configured on a VXLAN VLAN, then broadcast, unknown unicast, and unknown multicast (BUM) traffic received from the tunnel are copied to CPU. However, sending unknown unicast and unknown multicast traffic to CPU is unnecessary and could have negative side effects. Specifically, these packets take the L2Broadcast CoPP queue to the CPU. When there is a lot of unknown unicast and unknown multicast traffic, important broadcast traffic such as ARP may get dropped in the L2Broadcast CoPP queue. Further, this might also disrupt other control plane protocols such as BFD, BGP, etc.