VSRP and MRP signaling

A device may connect to an MRP ring through VSRP to provide a redundant path between the device and the MRP ring. VSRP and MRP signaling ensures rapid failover by flushing MAC addresses appropriately. The host on the MRP ring learns the MAC addresses of all devices on the MRP ring and VSRP link. From these MAC addresses, the host creates a MAC database (table), which is used to establish a data path from the host to a VSRP-linked device. The following figure below shows two possible data paths from the host to Device 1.

Figure 1. Two data paths from host on an MRP ring to a VSRP-linked device

If a VSRP failover from master to backup occurs, VSRP needs to inform MRP of the topology change; otherwise, data from the host continues along the obsolete learned path and never reach the VSRP-linked device, as shown in the following figure.

Figure 2. VSRP on MRP rings that failed over

A signaling process for the interaction between VSRP and MRP ensures that MRP is informed of the topology change and achieves convergence rapidly. When a VSRP node fails, a new VSRP master is selected. The new VSRP master finds all MRP instances impacted by the failover. Then each MRP instance does the following:

  • The MRP node sends out an MRP PDU with the mac-flush flag set three times on the MRP ring.
  • The MRP node that receives this MRP PDU empties all the MAC entries from its interfaces that participate on the MRP ring.
  • The MRP node then forwards the MRP PDU with the mac-flush flag set to the next MRP node that is in forwarding state.

The process continues until the Master MRP node secondary (blocking) interface blocks the packet. Once the MAC address entries have been flushed, the MAC table can be rebuilt for the new path from the host to the VSRP-linked device as shown in the following figure.

Figure 3. New path established

There are no CLI commands used to configure this process.