User Manual

242
Users Manual of XGS-6350-24X4C
26.1.4 Fast Ethernet Ring Protection Mechanism
26.1.4.1 Ring Detection and Control of Master Node
The master node transmits the HEALTH packets to the control VLAN through the primary port in a
configurable period. In normal case, the HEALTH packets will pass through all other nodes of the ring network
and finally arrive at the secondary port of the master node.
The secondary port blocks all data VLANs in primitive condition. When receiving the HEALTH packets
continuously, the secondary port keeps blocking data VLANs and blocking the loop. If the secondary port
does not receive the HEALTH packets from the primary port in a certain time (which can be configured), it will
regard the ring network is out of effect. Then the master node removes the blocking of data VLANs on the
secondary port, ages the local MAC address table, and transmits the RING-DOWN-FLUSH-FDB packets to
notify other nodes.
If the master node receives the HEALTH packets at the secondary port that is open to data VLANs, the ring
network is resumed. In this case, the master node immediately blocks data VLANs on the secondary port,
updates the local topology information and reports other nodes to age the MAC address table through
RING-UP-FLUSH-FDB packets.
You can configure related commands on the Hello-time node and the Fail-time node to modify the interval for
the primary port to transmit the HEALTH packets and the time limit for the secondary port to wait for the
HEALTH packets.
26.1.4.2 Notification of Invalid Link of Transit Node
After the transit port of the transit node is out of effect, the LINK-DOWN packet will be immediately transmitted
by the other transit port to notify other nodes. In normal case, the packet passes through other transit nodes
and finally arrives at one port of the master node.
After the master node receives the LINK-DOWN packet, it thinks that the ring network is invalid. In this case,
the master node removes the blocking of data VLANs on its secondary port, ages the local MAC address
table, transmits the RING-DOWN-FLUSH-FDB packet and notifies other nodes.
26.1.4.3 Resuming the Link of the Transit Node
After the transit port is resumed, it does not immediately transmit the packets of data VLANs, but enters the
Pre-Forwarding state. A transit port in pre-forwarding state only transmits and receives the control packets
from the control VLAN.
If there is only one transit port invalid in the ring network and when the port enters the pre-forwarding state,
the secondary port of the master node can receive the HEALTH packet from the primary port again. In this
case, the master node blocks data VLANs on the secondary port again and transmits the notification of
ageing address table outside. After the node with a transit port in pre-forwarding state receives the notification
of aging address table, the node will first modify the pre-forwarding port to the forwarding port and then ages
the local MAC address table.