Configuring Metro Features
December 2005 © Foundry Networks, Inc. 8 - 5
Metro Ring Protocol (MRP)
The Metro Ring Protocol (MRP) is a Foundry 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 (MANs) 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.
Figure 8.1 shows an example of an MRP metro ring.
Figure 8.1 Metro ring – normal state
The ring in this example consists of four MRP nodes (Foundry 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
Per vlan free ports The ports that are not controlled by the Layer 2 protocol information in
the master VLAN.
Table 8.2: CLI Display of Topology Group Information (Continued)
This Field... Displays...
F
F
F
B
F
Switch D
F
F
Customer A
F
F
F
F
F
This interface blocks
Layer 2 traffic
to prevent a loop
Switch A
Switch B
Master
Node
Customer ACustomer A
Customer A
Switch C
To Next Page
Loading...
Need help?
General
