The following figure shows an example of split horizon groups used to prevent communication between two access SAPs and between two access-uplink SAPs.
Using 7210 SAS-1 as an example:
Split horizon group ‟access” is created to prevent any communication between the SAP part of port 1/1/4 and port 1/1/5 (configured as access port) within the same VPLS.
Split horizon group ‟access uplink” is created to prevent any communication between SAP part of port 1/1/1 and port 1/1/3 (configured as an access-uplink) within the same VPLS.
VPLS 100 is created on 7210 SAS-1 with SAPs 1/1/1, 1/1/3, and SAPs on 1/1/4 and 1/1/5 as part of this VPLS. CE1, CE2 and CE3 are the customer sites.
With this configuration, any communication between ports 1/1/4 and 1/1/5 gets blocked, similarly communication between ports 1/1/1 and 1/1/3 gets blocked but any traffic received on ports (SAPs) part of split horizon group ‟access uplink” will be switched to ports (SAPs) part of split horizon group ‟access” and vice versa based on the FDB entries for VPLS 100.