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Ethernet OAM Support for Service VLANs Overview

You can enable propagation of the Ethernet IEEE 802.1ag Operation, Administration, and Maintenance (OAM) state of a static single-tagged service VLAN (S-VLAN) to a dynamic or static double-tagged customer VLAN (C-VLAN) and, by extension, to the subscriber interfaces configured on the C-VLAN. The static S-VLAN logical interface must be configured on a Gigabit Ethernet, 10-Gigabit Ethernet, or aggregated Ethernet physical interface.

Propagation of the S-VLAN OAM state to associated C-VLANs ensures that when the OAM state of the S-VLAN link is down, the associated C-VLANs and all subscriber interfaces configured on the C-VLANs are brought down as well.

Ethernet OAM Support for Service VLANs Terms and Acronyms

Table 1 defines the basic terms and acronyms used in this discussion of Ethernet OAM support for service VLANs.

Table 1: Ethernet OAM Support for Service VLANs Terms and Acronyms

Term

Definition

CFM

Connectivity fault management. Provides end-to-end monitoring of an Ethernet network that can be made up of one or more service instances. Junos OS supports Ethernet IEEE 802.1ag CFM.

Continuity check protocol

A feature of Ethernet IEEE 802.1ag CFM that provides fault detection within a maintenance association.

C-VLAN

Customer VLAN. A dynamic or static double-tagged logical interface that has both an outer VLAN tag (corresponding to the S-VLAN) and an inner VLAN tag (corresponding to the C-VLAN). In a 1:1 subscriber network access model, dedicated C-VLANs provide a one-to-one correspondence between an individual subscriber and the VLAN encapsulation.

OAM

Operation, Administration, and Maintenance. A set of Ethernet connectivity specifications and functions providing connectivity monitoring, fault detection and notification, fault verification, fault isolation, loopback, and remote defect identification. Ethernet interfaces on MX Series routers support the IEEE 802.1ag standard for OAM.

S-VLAN

Service VLAN. A static single-tagged logical interface that has only one outer VLAN tag (corresponding to the S-VLAN). In an N:1 subscriber network access model, S-VLANs are dedicated to a particular service, such as video, voice, or data, instead of to a particular subscriber. Because an S-VLAN is typically shared by many subscribers within the same household or in different households, it provides a many-to-one correspondence between individual subscribers and the VLAN encapsulation.

VLAN

Virtual local area network. A logical group of network devices that appear to be on the same local area network, regardless of their physical location.

Components of Ethernet OAM Support for Service VLANs

Ethernet OAM support for S-VLANs involves the following components:

  • Physical interface—On MX Series routers with Modular Port Concentrator/Modular Interface Card (MPC/MIC) interfaces, you can enable propagation of the S-VLAN OAM state to a C-VLAN on Gigabit Ethernet, 10-Gigabit Ethernet, or aggregated Ethernet physical interfaces.

  • S-VLAN—To enable propagation of the S-VLAN Ethernet OAM state to associated C-VLANs and subscriber interfaces, configure the static single-tagged S-VLAN logical interface to run the Ethernet IEEE 802.1ag CFM continuity check protocol.

  • C-VLAN—The C-VLAN is a dynamic or static double-tagged logical interface that has the same S-VLAN (outer) tag as the static single-tagged S-VLAN logical interface. If propagation of the S-VLAN OAM state to the C-VLAN is enabled on the physical interface, the router brings down the C-VLAN and its associated subscriber interfaces when the CFM continuity check protocol detects that the OAM state of the underlying S-VLAN is down.

  • Subscriber interfaces—Propagation of the S-VLAN Ethernet OAM state to associated C-VLANs and subscriber interfaces applies to all dynamic or static DHCP, IP demultiplexing (IP demux), and PPPoE subscriber interfaces configured on the C-VLAN.

How Ethernet OAM Support for Service VLANs Works

To enable propagation of the Ethernet OAM state of the S-VLAN to associated C-VLANs and subscriber interfaces, use the oam-on-svlan statement when you configure a Gigabit Ethernet (ge), 10-Gigabit Ethernet (xe), or aggregated Ethernet (ae) physical interface.

If Ethernet IEEE 802.1ag CFM is properly configured on the S-VLAN logical interface, including the oam-on-svlan statement for these Ethernet interfaces causes the router to bring down both of the following when the CFM continuity check protocol detects that the OAM state of the S-VLAN logical interface is down:

  • All dynamic or static double-tagged C-VLAN logical interfaces that have the same S-VLAN (outer) tag as the S-VLAN logical interface on which they are configured.

  • All dynamic or static DHCP, IP demux, and PPPoE logical subscriber interfaces configured on the associated C-VLANs.

To illustrate how Ethernet OAM support for S-VLANs works, consider the following sample configuration on a Gigabit Ethernet physical interface:

  • Gigabit Ethernet physical interface ge-1/0/3 configured with the svlan-on-oam statement.

  • Static single-tagged S-VLAN logical interface ge-1/0/3.0, which has a single S-VLAN outer tag, VLAN ID 600.

  • Ethernet OAM CFM protocol configured on the static S-VLAN logical interface. The CFM configuration includes an action profile with the interface-down default action to bring down the C-VLAN and dynamic subscriber interfaces when the continuity check protocol detects that the Ethernet OAM state of S-VLAN interface ge-1/0/3.0 is down.

  • Static double-tagged C-VLAN logical interface ge-1/0/3.100, which has an S-VLAN outer tag, VLAN ID 600, and a C-VLAN inner tag, VLAN ID 1.

  • Static PPPoE subscriber interfaces configured on C-VLAN interface ge-1/0/3.100.

Because the S-VLAN and C-VLAN logical interfaces in this example have the same S-VLAN outer tag (VLAN ID 600), the router brings down the C-VLAN interface and the PPPoE logical subscriber interfaces when the CFM continuity check detects that the OAM status of S-VLAN interface ge-1/0/3.0 is down.

Restrictions for Using Ethernet OAM Support for Service VLANs

Ethernet OAM support for S-VLANs is not currently supported for use with any of the following:

  • Dynamically configured S-VLAN logical interfaces

  • S-VLAN trunk interfaces

  • C-VLAN trunk interfaces

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