Double Forced Switch

A local FS is of a higher priority than a received R-APS (FS); therefore, the local FS request blocks the port even when the node receives a R-APS(FS) from another FS request of another node.

After the first FS clears, the node starts the guard timer and sends out a R-APS (NR). The adjacent nodes of the first cleared FS node will not process or forward the R-APS (NR) because they are still receiving R-APS (FS) from the second FS node. When the first FS node receives R-APS (FS) from the second FS nodes, it unblocks any blocked port and stops transmitting any lower priority R-APS messages. At this point, the topology follows the single FS process, as previously described.