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Example: Configure Ethernet CFM on Physical Interfaces

This example shows the configuration of Ethernet connectivity fault management (CFM) on physical interfaces.


This example uses the following hardware and software components:

  • Junos OS Release 9.3 or later.


CFM can be used to monitor the physical link between two routers. This functionality is similar to that supported by the IEEE 802.3ah LFM protocol.

In Junos OS Release 9.3 and later, CFM also supports aggregated Ethernet interfaces. On interfaces configured on Modular Port Concentrators (MPCs) and Modular Interface Cards (MICs) on MX Series routers, CFM is not supported on untagged aggregated Ethernet member links. MPCs and MICs do support CFM on untagged and tagged aggregated Ethernet logical interfaces.


The configurations in this example are only partial examples of complete and functional router configurations. Do not copy these configurations and use them directly on an actual system.


In the following example, two routers (Router 1 and Router 2) are connected by a point-to-point Gigabit Ethernet link. The link between these two routers is monitored using CFM. This is shown in Figure 1. The single boundary is a “down mep” in CFM terminology.

Figure 1: Ethernet CFM on Physical InterfacesEthernet CFM on Physical Interfaces

To configure Ethernet CFM on physical interfaces, perform these tasks:

CLI Quick Configuration

Router 1

Configure the interface and CFM:

The configuration on Router 2 mirrors that on Router 1, with the exception of the mep-id.

Router 2

Configure the interface and CFM:

To verify that the physical interface is configured correctly for CFM, use the show interface command. To verify the CFM configuration, use one or more of the show oam ethernet connectivity-fault-management commands listed in the CLI Explorer.