Cisco ASR 920 series Configuration Guide Ethernet Router

Maintenance Point
A maintenance point is a demarcation point on an interface (port) that participates in 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, MEPs and MIPs.
Maintenance Endpoints
Maintenance endpoints (MEPs) have the following characteristics:
•
Per maintenance domain (level) and service (S-VLAN or EVC)
•
At the edge of a domain, define the boundary
•
Within the bounds of a maintenance domain, confine CFM messages
•
When configured to do so, proactively transmit Connectivity Fault Management (CFM) continuity check
messages (CCMs)
•
At the request of an administrator, transmit traceroute and loopback messages
Inward Facing MEPs
Inward facing means the MEP communicates through the Bridge Relay function and uses the Bridge-Brain
MAC address. An inward facing MEP performs the following functions:
•
Sends and receives CFM frames at its level through the relay function, not via the wire connected to the
port on which the MEP is configured.
•
Drops all CFM frames at its level (or lower level) that come from the direction of the wire.
•
Processes all CFM frames at its level coming from the direction of the relay function.
•
Drops all CFM frames at a lower level coming from the direction of the relay function.
•
Transparently forwards all CFM frames at its level (or a higher level), independent of whether they come
in from the relay function side or the wire side.
A MEP of level L (where L is less than 7) requires a MIP of level M > L on the same port; hence, CFM
frames at a level higher than the level of the MEP will be catalogued by this MIP.
Note
•
If the port on which the inward MEP is configured is blocked by Spanning-Tree Protocol, the MEP can
no longer transmit or receive CFM messages.
Outward Facing MEPs for Port Channels
Outward facing means that the MEP communicates through the wire. Outward facing MEPs can be configured
on port channels (using cross connect functionality). A MIP configuration at a level higher than the level of
the outward facing MEP is not required.
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
129
Configuring Ethernet Connectivity Fault Management in a Service Provider Network
Maintenance Point

Cisco ASR 920 series Specifications

General

Brand	Cisco
Model	ASR 920 series
Category	Network Router
Language	English