Alcatel-Lucent 7210 SAS M Service Manual page 262

VPLS Features
Split Horizon SAP Groups and Split Horizon Spoke SDP Groups
Note: Split Horizon group is supported only on 7210 SAS-M devices configured in Network
mode.
Within the context of VPLS services, a loop-free topology inside a fully meshed VPLS core is
achieved by applying a split-horizon forwarding concept .The packets received from a mesh SDP
are never forwarded to other mesh SDPs within the same service. The advantage of this approach
is that no protocol is required to detect loops within the VPLS core network.
In applications such as DSL aggregation, it is useful to extend this split-horizon concept also to
groups of SAPs and/or spoke SDPs. This extension is referred to as a split horizon SAP group .
Traffic arriving on a SAP or a spoke SDP within a split horizon group will not be forwarded to
other SAPs and spoke SDPs configured in the same split horizon group, but will be forwarded to
other SAPs/spoke SDPs, which are not part of the split horizon group.
Configuration Guidelines for use of Split Horizon Group in a VPLS Service
In 7210 SAS devices, mesh SDPs cannot be configured in a service which uses split horizon
group. Conversely, if a service has a mesh-sdp configured, split horizon group cannot be used in
the same service.
Only one split horizon group per service is allowed for use.
Page 262 7210 SAS M Services Guide