Link Down Message Sent By A Transit Node; Ring Port Down Event Sent By Hardware Layer - Extreme Networks ExtremeWare XOS Guide Manual

Ethernet Automatic Protection Switching
A master node detects a ring fault in one of three ways:

Link down message sent by a transit node

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Ring port down event sent by hardware layers
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Polling response
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Link Down Message Sent by a Transit Node
When any transit node detects a loss of link connectivity on any of its ring ports, it immediately sends a
"link down" message on the control VLAN using its good link to the master node.
When the master node receives the "link down" message (see
"failed" state and opens its logically blocked secondary port on all the protected VLANs. Now, traffic
can flow through the master's secondary port. The master node also flushes its FDB and sends a
message on the control VLAN to all of its associated transit nodes to flush their forwarding databases as
well, so that all of the switches can learn the new paths to Layer 2 endstations on the reconfigured ring
topology.
Figure 15: EAPS fault detection and protection switching
S3 sends "link down"
message to
master node

Ring Port Down Event Sent by Hardware Layer

When a ring port goes down on a master node switch, it is notified by the lower hardware layer and
immediately goes into a "failed" state.
If the ring port that goes down on the master node is the primary port, the secondary port is opened.
The normal operation of flushing the master node's FDB and sending a "flush FDB" message to all
transit nodes is performed.
ExtremeWare XOS 11.1 Concepts Guide
Break
in ring
S 4
S 3
S 2
P S
S 1
Figure 15), it immediately declares a
S4 sends "link down"
message to master node
S 5
S 6
Master node opens secondary port
to allow traffic to pass
Master
node
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