BigIron RX Series Configuration Guide 41753-1002253-01Ring initialization for shared interfaces 14Flow when a link breaksIf the link between shared interfaces breaks (Figure 74), the secondary interface on Ring 1’smaster node changes to a preforwarding state. The RHP packet sent by port 3/1 on Ring 2 isforwarded through the interfaces on S4, then to S2. The packet is then forwarded through S2 to S3,but not from S2 to S1 since the link between the two nodes is not available. When the packetreaches Ring 1’s master node, the packet is forwarded through the secondary interface since it iscurrently in a preforwarding state. A secondary interface in preforwarding mode ignores any RHPpacket that is not from its ring. The secondary interface changes to blocking mode only when theRHP packet forwarded by its primary interface is returned.The packet then continues around Ring 1, through the interfaces on S1 to Ring 2 until it reachesRing 2’s master node. Port 3/2, the secondary interface on Ring 2 changes to blocking mode sinceit received its own packet, then blocks the packet to prevent a loop.FIGURE 74 Flow of RHP packets when a link for shared interfaces brakesRHP packets follow this flow until the link is restored; then the RHP packet returns to it normal flowas shown in Figure 74.NOTEThere should always be a layer 2 protocol configured in the default VLAN when MRP is configuredwith all dual mode ports.Configuring MRP with shared interfacesMRP Phase 2 allows you to enter commands such as the following when configuring MRP.XRing 1 Ring 2S3 S4S1S2111111 112222 22221,21,2Master nodeport2/2 changesto preforwarding(primary interface) port2/1Master nodeport3/2port3/1 (primary interface)= Ring 2 RHP packetTT
