Extreme Networks Summit Summit24, Installation And User Manual

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122 Summit24e3 Switch Installation and User Guide
Ethernet Automatic Protection Switching
Figure 23: EAPS fault detection and protection switching
A master node detects a ring fault in either of two ways:
• Polling response
•
Trap message sent by a transit node
Polling
The master node transmits a health-check packet on the control VLAN at a user-configurable interval
(see Figure 22). If the ring is complete, the master node will receive the health-check packet on its
secondary port (the control VLAN is not blocked on the secondary port). When the master node
receives the health-check packet, it resets its fail-period timer and continues normal operation.
If the master node does not receive the health-check packet before the fail-period timer expires, it
declares a “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 forwarding
database (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 end
stations on the reconfigured ring topology.
Trap 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 Figure 23), it immediately declares a
“failed” state and performs the same steps described above; it unblocks its secondary port for access by
the protected VLANs, flushes its FDB, and sends a “flush FDB” message to its associated transit nodes.
EW_072
S3 sends "link down"
message to
master node
Master
node
Break
in ring
Master node opens secondary port
to allow traffic to pass
S4 sends "link down"
message to master node
S 4
S 5
S 6
S 3
S 2
S 1
P S