A method and apparatus is provided for automatic protection switching in a ring
network by creating a protection domain having a control vlan and protected data
vlans and designating a master node and transit nodes connected by a primary port
and a secondary port. The master node blocks the secondary port for data vlan traffic
until it detects a fault either by notice from a transit node or by polling. When
a fault is detected, the master node unblocks the secondary port for data vlan
traffic. When the fault is restored, the transit node temporarily blocks the restored
port to data vlan traffic thereby preventing a loop. Each time the secondary port
is blocked and unblocked, the forwarding databases on all the nodes are flushed.