Each Ethernet Ring Node (ERN) in a major ring must have explicitly defined left and right interfaces so that ERP can function correctly.
For proper operation you must configure the interfaces following the same manner on each ERN, such as left/ right, left/ right, and so on.
The following example configures a left and right interface for a major ring.
device# configure terminal device(config)# erp 1 device(config-erp-1)# right-interface vlan 2 ethernet 1/2 device(config-erp-1)# left-interface vlan 2 ethernet 1/1
ERNs in a sub-ring must have at least one interface (either left or right) configured as shown below so that ERP can function correctly. The following example configures a right interface for a sub-ring.
device# configure terminal device(config)# erp 2 device(config-erp-2)# right-interface vlan 2 ethernet 1/1 device(config-erp-2)# sub-ring parent-ring-id 1