Fault Detection And Recovery - Extreme Networks Summit 200-24 Installation And User Manual

Fault Detection and Recovery

EAPS fault detection on a ring is based on a single control VLAN per EAPS domain. This EAPS domain
provides protection to one or more data-carrying VLANs called protected VLANs.
The control VLAN is used only to send and receive EAPS messages; the protected VLANs carry the
actual data traffic. As long as the ring is complete, the EAPS master node blocks the protected VLANs
from accessing its secondary port.
NOTE
The control VLAN is not blocked. Messages sent on the control VLAN must be allowed into the switch
for the master node to determine whether the ring is complete.
Figure 26: EAPS fault detection and protection switching
S3 sends "link down"
message to
master node
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 25). 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
Summit 200 Series Switch Installation and User Guide
Break
in ring
S 4
S 3
S 2
P S
S 1
S4 sends "link down"
message to master node
S 5
S 6
Master node opens secondary port
to allow traffic to pass
Master
node
Overview of the EAPS Protocol
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