Juniper ACX1000 Configuration Manual page 1185

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Chapter 34: Configuring Operations, Administration, and Management (OAM)
CFM partitions the service network into various administrative domains. For example,
operators, providers, and customers might be part of different administrative domains.
Each administrative domain is mapped into one maintenance domain providing enough
information to perform its own management, thus avoiding security breaches and making
end-to-end monitoring possible. Each maintenance domain is associated with a
maintenance domain level from 0 through 7. Level allocation is based on the network
hierarchy, where outermost domains are assigned a higher level than the innermost
domains.
Customer end points have the highest maintenance domain level. In a CFM maintenance
domain, each service instance is called a maintenance association. A maintenance
association can be thought as a full mesh of maintenance endpoints (MEPs) having
similar characteristics. MEPs are active CFM entities generating and responding to CFM
protocol messages.
There is also a maintenance intermediate point (MIP), which is a CFM entity similar to
the MEP, but more passive (MIPs only respond to CFM messages).
MEPs can be up MEPs or down MEPs. A link can connect a MEP at level 5 to a MEP at
level 7. The interface at level 5 is an up MEP (because the other end of the link is at MEP
level 7), and the interface at level 7 is a down MEP (because the other end of the link is
at MEP level 5).
In a Metro Ethernet network, CFM is commonly used at two levels:
By the service provider to check the connectivity among its provider edge (PE) routers
By the customer to check the connectivity among its customer edge (CE) routers
NOTE: The configured customer CFM level must be greater than service
provider CFM level.
In many Metro Ethernet networks, CFM is used to monitor connectivity over a VPLS and
bridge network.
NOTE: In ACX Series routers, VPLS is supported only on ACX5048 and
ACX5096 routers.
Ethernet Operations, Administration, and Maintenance
Example: Configuring Ethernet CFM on Bridge Connections
Example: Configuring Ethernet CFM on Physical Interfaces
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