Supported Platforms
Related Documentation
- ACX, M, MX, T Series
- connectivity-fault-management
- Creating the Maintenance Domain
- Configuring Maintenance Intermediate Points
- Creating a Maintenance Association
- Continuity Check Protocol
- Configuring a Maintenance Endpoint
- Configuring a Connectivity Fault Management Action Profile
- Configuring Linktrace Protocol in CFM
- Configuring Ethernet Local Management Interface
- Configuring Port Status TLV and Interface Status TLV
- Configuring Rate Limiting of Ethernet OAM Messages
- Configuring 802.1ag Ethernet OAM for VPLS
- M, MX, T Series
- Configuring M120 and MX Series Routers for CCC Encapsulated Packets
- MX, T Series
- Configuring MAC Flush Message Processing in CET Mode
- Additional Information
- Junos® OS Ethernet Interfaces
IEEE 802.1ag OAM Connectivity Fault Management Overview
Ethernet interfaces on M7i and M10i routers with the Enhanced CFEB (CFEB-E) and on M120, M320, MX Series, T Series, and PTX Series routers support the IEEE 802.1ag standard for Operation, Administration, and Management (OAM). The IEEE 802.1ag specification provides for Ethernet connectivity fault management (CFM). The goal of CFM is to monitor an Ethernet network that may comprise one or more service instances. Junos OS supports IEEE 802.1ag connectivity fault management.
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
.
CFM
does not support Multichassis Link Aggregation (MC-LAG). Do not configure
the mc-ae statement when you configure CFM.
On T Series routers, CFM is not supported on
interfaces configured with CCC encapsulation. If you configure CFM,
the system displays the following message: “MEPs cannot be configured on ccc interface on this platform”.
Network entities such as operators, providers, and customers may be part of different administrative domains. Each administrative domain is mapped into one maintenance domain. Maintenance domains are configured with different level values to keep them separate. Each domain provides enough information for the entities to perform their own management, perform end-to-end monitoring, and still avoid security breaches.
![]() | Note: As a requirement for Ethernet OAM 802.1ag to work, distributed periodic packet management (PPM) runs on the Routing Engine and Packet Forwarding Engine by default. You can only disable PPM on the Packet Forwarding Engine. To disable PPM on the PFE, include the ppm no-delegate-processing statement at the [edit routing-options ppm] hierarchy level. |
IEEE 802.1ag OAM supports graceful Routing Engine switchover (GRES). IEEE 802.1ag OAM is supported on untagged, single tagged, and stacked VLAN interfaces.
Connectivity Fault Management Key Elements
Figure 1 shows the relationships among the customer, provider, and operator Ethernet bridges, maintenance domains, maintenance association end points (MEPs), and maintenance intermediate points (MIPs).
Figure 1: Relationship Among MEPs, MIPs, and Maintenance Domain Levels

![]() | Note: Maintenance intermediate points (MIP) are not supported on the ACX Series routers. |
A maintenance association is a set of MEPs configured with the same maintenance association identifier and maintenance domain level. Figure 2 shows the hierarchical relationships between the Ethernet bridge, maintenance domains, maintenance associations, and MEPs.
Figure 2: Relationship Among Bridges, Maintenance Domains, Maintenance Associations, and MEPs

Related Documentation
- ACX, M, MX, T Series
- connectivity-fault-management
- Creating the Maintenance Domain
- Configuring Maintenance Intermediate Points
- Creating a Maintenance Association
- Continuity Check Protocol
- Configuring a Maintenance Endpoint
- Configuring a Connectivity Fault Management Action Profile
- Configuring Linktrace Protocol in CFM
- Configuring Ethernet Local Management Interface
- Configuring Port Status TLV and Interface Status TLV
- Configuring Rate Limiting of Ethernet OAM Messages
- Configuring 802.1ag Ethernet OAM for VPLS
- M, MX, T Series
- Configuring M120 and MX Series Routers for CCC Encapsulated Packets
- MX, T Series
- Configuring MAC Flush Message Processing in CET Mode
- Additional Information
- Junos® OS Ethernet Interfaces
Published: 2013-01-11
Supported Platforms
Related Documentation
- ACX, M, MX, T Series
- connectivity-fault-management
- Creating the Maintenance Domain
- Configuring Maintenance Intermediate Points
- Creating a Maintenance Association
- Continuity Check Protocol
- Configuring a Maintenance Endpoint
- Configuring a Connectivity Fault Management Action Profile
- Configuring Linktrace Protocol in CFM
- Configuring Ethernet Local Management Interface
- Configuring Port Status TLV and Interface Status TLV
- Configuring Rate Limiting of Ethernet OAM Messages
- Configuring 802.1ag Ethernet OAM for VPLS
- M, MX, T Series
- Configuring M120 and MX Series Routers for CCC Encapsulated Packets
- MX, T Series
- Configuring MAC Flush Message Processing in CET Mode
- Additional Information
- Junos® OS Ethernet Interfaces