MAC pinning to prevent loops

A MAC move occurs when a MAC address frequently appears on a different physical interface than the one it was learned on. Frequent MAC moves indicate the presence of loops in Layer 2 bridges and in VPLS networks. To avoid loops, you can enable the MAC pinning feature on an interface. Support for MAC pinning is provided to prevent loops in Layer 2 bridges and in VPLS networks. When you enable MAC pinning on an interface in a bridge domain or VPLS domain, a MAC address learned over that interface cannot be relearned on any other interface in the same bridge domain or VPLS domain until the MAC address either ages out on the first interface or is cleared from the MAC table. If a packet with the same MAC address arrives at any other interface in the same bridge domain, then the packet is discarded. This action, effectively, controls MAC moves and prevents the creation of loops in Layer 2 bridges and VPLS domains.