C
HAPTER
14
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 507 –
◆ West/East – Connects to next ring node to the west/east.
Each node must be connected to two neighbors on the ring. For
convenience, the ports connected are referred to as east and west
ports. Alternatively, the closest neighbor to the east should be the next
node in the ring in a clockwise direction, and the closest neighbor to the
west should be the next node in the ring in a counter-clockwise
direction.
◆ Interface – The port or trunk attached to the west or east ring port.
Note that a ring port cannot be configured as a member of a spanning
tree, a dynamic trunk, or a static trunk.
◆ Port State – Once configured, this field shows the operational state of
the ring ports for this node:
â–
Blocking – The transmission and reception of traffic is blocked and
the forwarding of R-APS messages is blocked, but the transmission
of locally generated R-APS messages is allowed and the reception of
all R-APS messages is allowed.
â–
Forwarding – The transmission and reception of traffic is allowed;
transmission, reception and forwarding of R-APS messages is
allowed.
â–
Unknown – The interface is not in a known state.
◆ Local SF – Shows if a signal fault exists on a link to the local node.
◆ Local FS – Shows if a forced switch command was issued on this
interface.
◆ Local MS – Shows if a manual switch command was issued on this
interface.
◆ MEP – Specifies the CCM MEPs used to monitor the link on a ring node.
If a MEP is used to monitor the link status of an ERPS node with CFM
continuity check messages, then the MEG Level parameter on this
configuration page must match the authorized maintenance level of the
CFM domain to which the specified MEP belongs. (See "Configuring CFM
Maintenance Domains" on page 521.)
To ensure complete monitoring of a ring node, specify the CFM MEPs
used to monitor both the east and west ports of the ring node.
If CFM determines that a MEP node which has been configured to
monitor a ring port with this command has gone down, this information
is passed to ERPS, which in turn processes it as a ring node failure. For
more information on how ERPS recovers from a node failure, refer to
the description of the Revertive parameter on this configuration page.
◆ RPL – If node is connected to the RPL, this shows by which interface.
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