Allied Telesis AT-9900, RAPIER I, X900-48FE, AT-8900, AT-8700XL, AT-8600 Restoring Normal Operation

6 Software Reference

Restoring Normal Operation

Transit Nodes

Once a fault in the ring or node has been rectified, the transit nodes that span the (previously) faulty link section will detect that link connectivity has returned. They will then move their appropriate ring port state, from “Links-Down” to “Pre-Forwarding,” and await the “Ring-Up-Flush” control message from the master node. See “Master Node” on page 1-6.

Once these transit nodes receive the “Ring-Up-Flush” message, they:

■flush their forward databases for both their ring ports

■change the state of their ports from blocking to forwarding, which allows data to flow through their previously blocked ring ports

Note that the transit nodes do not enter the forward state until they have received the “Ring-Up-Flush” message. This is to prevent the possibility of a loop condition occurring caused by the transit nodes moving into the forwarding state before the master node secondary port is able to return to the blocking state. During such a period, the ring would have no ports blocked.

Master Node

With the link restored, the healthcheck messages that are sent from the primary port of the master node now complete the loop and arrive at the master node’s secondary port. The master node now takes the following steps to restore normal conditions:

■declares the ring to be in a “complete” state

■blocks its secondary port for data (non-control) traffic

■flushes its forwarding database for its two ring ports

■sends a “Ring-Up-Flush-FDB” message from its primary port, to all transit nodes.