ERN roles

In an Ethernet ring topology you can assign each ERN one of three roles:

• Ring Protection Link Owner (RPL owner) -- One RPL owner must exist in each ring; its role is to prevent loops by maintaining a break in traffic flow to one configured link while no failure condition exists within the ring.
• Non-RPL node -- Multiple non-RPL nodes, can exist in a ring; but they have no special role and perform only as ring members. Ring members apply and then forward the information received in R-APS messages.
• Ring Protection Link (RPL) node -- RPL nodes block traffic to the segment that connects to the blocking port of the RPL owner. The RPL node is used in dual-end blocking and is part of the FDB optimization feature.

Each device can only have one role at any time. Non-ERN devices can also exist in topologies that use IEEE 802.1ag.