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Allied Telesis AT 9924SP AT-9924SP-30 AT-9924SP-30 Software Manual page 44

Configure epsr (ethernet protection switching ring) to protect a ring from loops

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4. Port 1 comes back up
The transit node detects that port 1 has come back up. It sends a trap and changes the EPSR
state to Pre-forwarding. Note that it leaves port 1 blocked for vlan2, to make sure there are
no loops.
Manager 9924-B>
Block EPSR:test port:1 VLAN:2
EPSR test, Port 1 port up
EPSR INFO: Send trap EPSR:test oldState:LINK-DOWN newState:PRE-FORWARDING
EPSR test oldState:LINK-DOWN newState:PRE-FORWARDING
5. Transit node receives a Health message
Now that the master node's primary port is up again, it sends a Health message. Now that
the transit node's port 1 is up again for the control VLAN, the transit node receives the
message. This demonstrates that the transit node has only blocked port 1 for the data VLAN,
not the control VLAN. EPSR control messages never loop because the master node never
forwards them between its ring ports.
Note that the hello sequence number increments from the number it was before the primary
port went down, because the master node could not transmit Health messages while the
port was down.
This is the packet shown in step
Manager 9924-B>
EPSR Port1 Rx:
EPSR Port1 Rx:
-----------------------------------------------------------------------
-----------------------------------------------------------------------
Page 44 | AlliedWare™ OS How To Note: EPSR
nodeType:TRANSIT
00e02b00 00040000 cd280619 8100e3e8 005caaaa 0300e02b
00bb0100 00541dee 00000000 0000cd28 0619990b 00400105 03e80000
00000000 cd280619 00010002 020000fa
TYPE = HEALTH
CTRL VLAN = 1000
HELLO TIME = 1
HELLO SEQ = 250
8 on page 39
of the master node debug output.
STATE = FAILED
SYSTEM = 00-00-cd-28-06-19
FAIL TIME = 2
Debugging

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