Broadcast, unknown-unicast and multicast traffic

[3][4] Broadcast traffic is used to transmit a message to any reachable destination in the network without the need to know any information about the receiving party.

In this case the switch marks the frame for flooding and sends it to all forwarding ports within the respective VLAN.

[5] Flooding BUM frames is required in transparent bridging and in a data center context this does not scale well causing poor performance.

One issue that may arise is that some network devices cannot handle high rates of broadcast, unknown-unicast or multicast traffic.

In such cases, it is possible to limit the BUM traffic for specific ports in order to have a control on the number of packets or bytes that are flooded on the VLAN to other devices.

To prevent flooding unknown-unicast traffic across the switch, it is possible to configure the network equipment to divert unknown-unicast traffic to specific trunk interfaces in order to split broadcast coming from different VLANs or to use specific trunk interfaces for multiple VLANs.

Now, as with any other overlay network protocol, its scalability is tied into how well it can handle the Broadcast, Unknown unicast and Multicast (BUM).

Broadcast traffic is reduced and VXLAN tunnel endpoints (VTEPs) reply to the caller directly.