Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 484 –
ERPS Forced and
Manual Mode
Operations
Use the Administration > ERPS (Configure Operation) page to block a ring port
using Forced Switch or Manual Switch commands.
Parameters
These parameters are displayed:
◆ Domain Name – Name of a configured ERPS ring.
◆ Operation – Specifies a Forced Switch (FS) or Manual Switch (MS) operation on
the east or west ring port.
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Forced Switch – Blocks specified ring port. (Options: West or East)
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A ring with no pending request has a logical topology with the traffic
channel blocked at the RPL and unblocked on all other ring links. In this
situation, the FS command triggers protection switching as follows:
a. The ring node where an FS command was issued blocks the traffic
channel and R-APS channel on the ring port to which the
command was issued, and unblocks the other ring port.
b. The ring node where the FS command was issued transmits R-APS
messages indicating FS over both ring ports. R-APS (FS) messages
are continuously transmitted by this ring node while the local FS
command is the ring node’s highest priority command (see
Table 30 on page 485). The R-APS (FS) message informs other ring
nodes of the FS command and that the traffic channel is blocked on
one ring port.
c. A ring node accepting an R-APS (FS) message, without any local
higher priority requests unblocks any blocked ring port. This action
subsequently unblocks the traffic channel over the RPL.
d. The ring node accepting an R-APS (FS) message, without any local
higher priority requests stops transmission of R-APS messages.
e. The ring node receiving an R-APS (FS) message flushes its FDB.
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Protection switching on a forced switch request is completed when the
above actions are performed by each ring node. At this point, traffic
flows around the ring are resumed. From this point on the following
rules apply regarding processing of further forced switch commands:
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While an existing forced switch request is present in a ring, any new
forced switch request is accepted, except on a ring node having a
prior local forced switch request. The ring nodes where further
forced switch commands are issued block the traffic channel and R-
APS channel on the ring port at which the forced switch was issued.
The ring node where the forced switch command was issued
transmits an R-APS message over both ring ports indicating FS. R-
APS (FS) messages are continuously transmitted by this ring node
while the local FS command is the ring node’s highest priority
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