IP Neighbor Flood Overview

When a port goes down, L3 traffic to a neighbor will get dropped until the MAC address is learned on the new port. Source MAC learning could take a while, and this learning could be dependent on traffic being successfully delivered to the client.

An example is when wireless clients are connected through access points balanced across several wireless controllers connected to Halon switches. Traffic to clients is dropped when the port connecting the controller and switch goes down.

The port can go down when the wireless controller goes down and reboots. Access points are adopted by other controllers on the network to avoid traffic drop for the wireless clients, but the back-end data plane requires handling.

During such failover conditions in scaled setups, MAC learning could take a while, and significant traffic loss can occur.

The solution is to flood traffic on the VLAN so that traffic reaches the hosts.

Once neighbors are relearned over a new port on the same VLAN, the switch will stop flooding.

IP Neighbor Flood is supported on SVIs. It is disabled by default.