Interface And Hardware Component Configuration Guide For Cisco Ncs 5500 Series Routers, Ios Xr Release - Cisco NCS 5500 Series Configuration Manual

Configuring Ethernet OAM
Ethernet CFM
This figure illustrates the monitored areas for Down and Up MEPs.
Figure 3: Monitored Areas for Down and Up MEPs
This figure shows maintenance points at different levels. Because domains are allowed to nest but not intersect
(see Figure 3), a MEP at a low level always corresponds with a MEP or MIP at a higher level. In addition,
only a single MIP is allowed on any interface—this is generally created in the lowest domain that exists at
the interface and that does not have a MEP.
CFM Maintenance Points at Different
Levels
MIPs and Up MEPs can only exist on switched (Layer 2) interfaces, because they send and receive frames
from the bridge relay function. Down MEPs can be created on switched (Layer 2) or routed (Layer 3) interfaces.
MEPs continue to operate normally if the interface they are created on is blocked by the Spanning Tree Protocol
(STP); that is, CFM frames at the level of the MEP continue to be sent and received, according to the direction
of the MEP. MEPs never allow CFM frames at the level of the MEP to be forwarded, so the STP block is
maintained.

Interface and Hardware Component Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release

6.1.x
30