CLI Reference Guide-R04

Chapter 21 | ERPS Commands
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continuously transmitted by this ring node while the local FS command is
the ring node’s highest priority command (see Table 99 on page 571). 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.
◆ 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:
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 command. As such, two or
more forced switches are allowed in the ring, which may inadvertently cause
the segmentation of an ring. It is the responsibility of the operator to prevent
this effect if it is undesirable.
Ring protection requests, commands and R-APS signals have the priorities as
specified in the following table.
Table 99: ERPS Request/State Priority
Request / State and Status Type Priority
Clear local highest
FS local |
R-APS (FS) remote |
local SF
*
local |
local clear SF local |
R-APS (SF) remote |
R-APS (MS) remote |
MS local |
WTR Expires local |
WTR Running local |