VLAN Table Configuration

By default there is a one-to-one relationship between a service ID and the CFM monitored service. If the service ID is 10 and the monitored CFM service is a VLAN, the monitored service is VLAN 10. In a one-to-one CFM service, the only monitored service is the primary service or selector. There are no other services associated with the primary service. The primary service can both receive and send CFM PDUs when the CFM device is a MEP. The primary service can receive CFM PDUs when the CFM device is a MIP. To fully monitor multiple services on the MEP would require that you create a separate service (MA) for each of the VLANs associated with a MEP adding considerable administrative overhead. When the primary goal is to fully monitor a single CFM service and, at the same time, monitor the reception of CFM PDUs on a group of associated services within a single MA, the VLAN table provides a significant reduction in administrative overhead.

The CFM VLAN table allows you to associate one or more services or selectors with the primary service. These services associated with the primary are capable of receiving CFM PDUs on any service configured in the VLAN table to which the monitored service belongs. For example: if the VLAN table for primary selector 10 has a configured selector list containing selectors 11 - 14, and the monitored service is a VLAN, MEPs with any primary VLAN of 10 through 14 will:

• Both receive and send CFM PDUs on the MEP‘s primary VLAN (the configured VID or the primary service configured for the MA if the MEP VID is set to 0)
• Receive CFM PDUs on any other VLAN table member configured on the device

VLAN Table Configuration Overview presents a VLAN table overview for an MA configured with a VLAN service and a VID of 10. The VLAN table is configured with a primary selector of 10 and associated selector list of 11 and 12. MEP0 and MEP2 are configured with the default VID 0 and inherit the MA VID setting 10. For these two MEPs, CFM PDUs are sent and received on VLAN 10 and received on VLANs 11 and 12. MEP1 and MEP3 are configured for VID 11. For these two MEPs, CFM PDUs are sent and received on VLAN 11 and received on VLANs 10 and 12. MEP4 is configured with VID 12. For MEP4, CFM PDUs are sent and received on VLAN 12 and received on VLANs 10 and 11.

The primary selector defines the ID of the service being modified. When configuring a CFM service, the configured VID for the new service is the primary selector. If the VID is configured for the default of 0, the MA the device belongs to provides the primary selector. If the device primary selector is a member of the VLAN table, all other members of the table are associated with the device primary selector.

When configuring the VLAN table, the primary selector is specified. One or more service IDs are specified in the selector list. Specifying the enable command option activates the association between the IDs in the selector list and the primary service. Specifying the disable command option disables the association of the IDs in the selector list with the primary service. The VLAN table remains configured, but is not active.

Maintenance points (MIP or MEP) associated with a CFM service will be able to receive CFM PDUs on any of the active IDs defined in the VLAN table selector list. MEPs may be configured with a Primary VID, which must belong to the enabled VLAN table, otherwise there is a one-to-one relationship between the VID and the service. With a primary VID defined, the MEP can transmit tagged PDUs using that primary service. If no primary VID is defined by the maintenance point, the VID, as inherited from the MA, will be used by the maintenance point to tag its transmitted PDUs.

Use the cfm vlan-table command in global configuration mode to configure a VLAN table.