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20 Description of the Ring Protocol
(b) Operation for each node in a backup ring
2. HC(S) sending is restarted.
The shared node that detected multi-fault recovery starts sending backup ring
HC(S)s again.
(2) Switchback operation from backup rings
The following figure shows switchback operation from a backup ring.
Figure 20-26 Switchback from backup rings
(a) Operation for each node in a backup ring
1. Ring restoration is detected due to reception of HC(S)s.
When the master node receives HC(S)s sent by shared nodes from both directions,
it determines that recovery from the ring fault has occurred, and performs restoration
operations. For details about operation for the master node and transit nodes when
recovery is detected, because operation is the same as for multi-rings, see (2)
Operation when recovery is detected in 20.4.3 Operation for faults and restoration
other than for shared links in a shared link non-monitoring ring.
(b) Operation for each node in a shared link monitoring ring
2. Flush control frames are sent from shared nodes.
When shared nodes receive a flush control frame from the master node of the
backup ring, they send to the shared link monitoring ring only flush control frames
that clear the MAC address table.
3. The MAC address table is cleared.
Transit nodes receive flush control frames sent from shared nodes, and clear the
MAC address table.
4. The Blocking status is maintained.
Blocking is maintained for the ring VLAN status of the ring ports after recovery from
the link fault, because the master node has not detected ring restoration.
For details about when Blocking is cleared, see (11) Communication during partial
multi-fault recovery in 20.7 Notes on Ring Protocol usage.
(3) Operation during recovery from a shared link fault
The following figure shows operation during shared link fault restoration.
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