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20 Description of the Ring Protocol
Figure 20-8 Operation during a ring fault
(1) Master node operation
A fault is determined to have occurred when health check frames in both directions are not
received within the pre-determined time. Switching operation is performed as follows on
the master node that detects the fault:
1. The VLAN status of the ring for data transfer is changed.
The ring VLAN status for the secondary port is changed from Blocking to Forwarding.
The ring VLAN status when a fault is detected is changed as shown in the following
table.
Table 20-2 VLAN status of rings for data transfer when a fault is detected
Ring port
Primary port
Secondary port
2. Flush control frames are sent.
Flush control frames are sent from the primary port and secondary port of the master
node.
3. The MAC address table is cleared.
The MAC address table entries pertaining to the ring port are cleared. Clearing the
MAC address table entries allows paths to be switched quickly.
4. The monitoring status is changed.
When a ring fault is detected, the master node changes from the fault monitoring
status to the recovery monitoring status.
(2) Transit node operation
The following operation is performed on a transit node that receives a flush control frame
sent from a master node detecting a fault:
5. Flush control frames are transferred.
Any received flush control frames are transferred to the next node.
6. The MAC address table is cleared.
The MAC address table entries pertaining to the ring port are cleared. Clearing the
360
Before (normal)
Forwarding
Blocking
After (fault)
Forwarding
Forwarding
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