Aliasing is the term used to describe the mechanism where a remote leaf node load balances all Layer 2 traffic using all the other leaf nodes that have the same ES towards a host device. For this load balancing to work, the leafs must be in the All-Active multi-homing mode where all the leaf nodes are allowed to forward traffic to and from the ES. When enabled, All-Active multi-homing mode allows a leaf node to advertise that the ESI it is on is reachable even if the remote leaf has not learnt any MAC address of the connected leafs for that ES.
A leaf node advertises that it is a member of an ES using the ES-AD route. When the MAC address is added to the forwarding table, the number of paths and VLAN/BD information is inferred from the AD-per-ES and AD-per-EVI routes.
A learned ES-AD route is removed when the last AD-per-ES route with the same ESI is withdrawn using the Mass Withdrawal mechanism.