Maintenance Points - Cisco ASR 920 Series Configuration Manual Ethernet Router

Maintenance Points

• Down (toward the wire) MEPs.
A domain can be removed when all maintenance points within the domain have been removed and all remote
MEP entries in the continuity check database (CCDB) for the domain have been purged.
Maintenance Points
A maintenance point (MIP) is a demarcation point on an interface or port that participates in Connectivity
Fault Management (CFM) within a maintenance domain. Maintenance points on device ports act as filters
that confine CFM frames within the bounds of a domain by dropping frames that do not belong to the correct
level. Maintenance points must be explicitly configured on Cisco devices. Two classes of maintenance points
exist, maintenance end points (MEPs) and MIPs. Support for MIPs varies by Cisco release.
Maintenance Association Endpoints
Maintenance association endpoints (MEPs) reside at the edge of a maintenance domain and confine Ethernet
Connectivity Fault Management (CFM) messages within the domain via the maintenance domain level. MEPs
periodically transmit and receive continuity check messages (CCMs) from other MEPs within the domain.
At the request of an administrator, linktrace and loopback messages can also be transmitted. MEPs are either
"Up" (toward the bridge) or "Down" (toward the wire). Support for Up MEPs varies by Cisco release.
When the continuity-check static rmep command is configured on a port MEP and continuity checking does
not detect a removed MEP, the port is set to MAC operation down and the interface protocol is set to down.
Normal traffic is stopped because the line protocol is down, but CFM packets still pass.
MEP configurations can be removed after all pending loopback and traceroute replies are removed and the
service on the interface is set to transparent mode.
Down MEPs for Routed Ports
Down MEPs communicate through the wire.
Down MEPs use the port MAC address.
A Down MEP performs the following functions:
• Sends and receives Ethernet CFM frames at its level via the wire connected to the port where the MEP
• Processes all Ethernet CFM frames at its level coming from the direction of the wire.
• Drops all Ethernet CFM frames at a lower level coming from the direction of the wire.
• Transparently drops all Ethernet CFM frames at a higher level, independent of whether they came in
Ethernet CFM Messages
Ethernet CFM uses standard Ethernet frames. Ethernet CFM frames are distinguishable by EtherType and for
multicast messages by MAC address. Ethernet CFM frames are sourced, terminated, processed, and relayed
by bridges. Routers can support only limited Ethernet CFM functions.
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
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is configured.
from the bridge or wire.
Configuring Ethernet CFM