C
HAPTER
14
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 510 –
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.
CLI REFERENCES
â—† "erps forced-switch" on page 1115
â—† "erps manual-switch" on page 1117
â—† "erps clear" on page 1115
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.
â–
Forced Switch – Blocks specified ring port.
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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 32 on page 511). 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:
â–
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
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