Metro Ring Protocol Overview

Metro Ring Protocol (MRP) is a RUCKUS proprietary protocol that prevents Layer 2 loops and provides fast reconvergence in Layer 2 ring topologies. It is an alternative to STP and is especially useful in Metropolitan Area Networks (MAN) where using STP has the following drawbacks:

  • STP allows a maximum of seven nodes. Metro rings can easily contain more nodes than this.
  • STP has a slow reconvergence time, taking many seconds or even minutes. MRP can detect and heal a break in the ring in sub-second time.

The following figure shows an example of an MRP metro ring.

Figure 1. Metro ring - normal state

The ring in this example consists of four MRP nodes (RUCKUS switches). Each node has two interfaces with the ring. Each node also is connected to a separate customer network. The nodes forward Layer 2 traffic to and from the customer networks through the ring. The ring interfaces are all in one port-based VLAN. Each customer interface can be in the same VLAN as the ring or in a separate VLAN.

One node is configured as the master node of the MRP ring. One of the two interfaces on the master node is configured as the primary interface; the other is the secondary interface. The primary interface originates Ring Health Packets (RHPs), which are used to monitor the health of the ring. An RHP is forwarded on the ring to the next interface until it reaches the secondary interface of the master node. The secondary interface blocks the packet to prevent a Layer 2 loops.