Unicast – communicate with a specfic device.
Broadcast – communicate with all devices whether they want to or not.
Multicast – communicate with many devices but only those who are interested.
L2 Anycast – “I don’t care” – several devices may be able to respond to communication but I will enter a unicast conversation with the first one that answers. Also works at L3 but this is determined by routing.
Anycast Gateways are essentially SVI’s in the traditional VLAN sense deployed on every edge node. The idea here being that endpoints don’t need to go across the entire fabric to reach their default gateway. Anycast allows the SVI’s to share the same IP address.
When an endpoint ARP’s out for the gateway IP address, a virtual MAC address is returned which is also shared allowing the client to roam seamlessly.
This is also known as a host pool which consists of an SVI address and mask.
