Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 465

How ring breaks are detected and healed 14 How ring breaks are detected and healed Figure 67 Shows the ring forwarding state following a link break. MRP quickly heals the ring and preserves connectivity among the customer networks. FIGURE 67 Metro ring - ring break Customer A F F F Switch B F F Customer A Switch C F Switch A Master Node F F Customer A Switch D F F Customer A If a break in the ring occurs, MRP heals the ring by changing the states of some of the ring interfaces: • Blocking interface - The Blocking interface on the Master node has a dead timer. If the dead time expires before the interface receives one of its ring's RHPs, the interface changes state to Preforwarding. Once the secondary interface changes state to Preforwarding: • If the interface receives an RHP, the interface changes back to the Blocking state and resets the dead timer. • If the interface does not receive an RHP for its ring before the Preforwarding time expires, the interface changes to the Forwarding state, as shown in Figure 67. • Forwarding interfaces - Each member interface remains in the Forwarding state. When the broken link is repaired, the link's interfaces come up in the Preforwarding state, which allows RHPs to travel through the restored interfaces and reach the secondary interface on the Master node. BigIron RX Series Configuration Guide 393 53-1001810-01