Ring initialization

The ring shown in Figure 1 shows the port states in a fully initialized ring without any broken links. Figure 1 shows the initial state of the ring, when MRP is first enabled on the ring switches. All ring interfaces on the master node and member nodes begin in the Preforwarding state (PF).

Figure 1. Metro ring - initial state

MRP uses Ring Health Packets (RHPs) to monitor the health of the ring. An RHP is an MRP protocol packet. The source address is the MAC address of the master node and the destination MAC address is a protocol address for MRP. The Master node generates RHPs and sends them on the ring. The state of a ring port depends on the RHPs.