Layer 2 control processing

Operators providing the Epipe service must be able to transparently forward Layer 2 control frames received from the customers. This allows their customers to run these control protocols between the different locations that are part of the Layer 2 VPN service. The 7210 SAS platforms provide the user with the following capability:

Note:

The CDP, VTP, DTP, PAgP, and UDLD management protocols are forwarded transparently in an Epipe service.

By default, LACP, LLDP, EFM OAM, and dot1x Layer 2 control protocol untagged packets are discarded if the protocol is not enabled on the port where these frames are received. The user has an option to enable peering by enabling the protocol on the port and configuring the appropriate parameters for the protocol. The user also has an option to tunnel these packets using an Epipe or VPLS service.

In a VPLS service, the Layer 2 control frames are sent out of all the SAPs configured in the VPLS service. Nokia recommends using this feature carefully and only when a VPLS is used to emulate an end-to-end Epipe service (that is, an Epipe configured using a three-point VPLS service, with one access SAP and two access-uplink SAPs or SDPs for redundant connectivity). That is, if the VPLS service is used for multipoint connectivity, it is not recommended to use this feature. When a Layer 2 control frame is forwarded out of a dot1q SAP or a QinQ SAP, the SAP tags of the egress SAP are added to the packet.

The following SAPs can be configured for tunneling the untagged L2CP frames (corresponding protocol tunneling needs to be enabled on the port):

In addition to the protocols listed previously, protocols that are not supported on the 7210 SAS (for example, GARP, GVRP, ELMI, and others) are transparently forwarded in case of a VPLS service. These protocols are transparently forwarded if a null SAP, dot1q default SAP, dot1q explicit null SAP or 0.* SAP is configured on the port and the received packet is untagged. If the received packet is tagged and matches the tag of any of the SAPs configured on the port, it is forwarded in the context of the SAP and the service. Otherwise, if the received packet is untagged and none of the null or dot1q default or dot1q explicit null or 0.* SAP is configured, it is discarded.

If a 7210 receives a tagged L2CP packet on any SAP (including null, dot1q, dot1q range, QinQ, QinQ default), it is forwarded transparently in the service similar to normal service traffic (xSTP processing behavior is different in VPLS service and is listed as follows).

The xSTP processing behavior in a VPLS service is as follows:

Parent topic: Services overview
1 Refer to the 7210 SAS-Mxp, R6, R12, S, Sx, T Interface Configuration Guide for more information about options available for LLDP tunneling.
2 L2TP support on 7210 SAS platforms varies among the platforms. Not all platforms support tunneling of all CISCO protocols. See L2PT and BPDU translation for more information.