Appendix: port-based split horizon

This section provides Port-Based Split Horizon configuration information.

Overview

Note:

This feature is only supported on the 7210 SAS-D and 7210 SAS-Dxp.

The port-based split horizon feature can be used to disable local switching on the 7210 SAS. A loop-free topology can be achieved using split horizon on 7210 SAS switches.

Traffic arriving on an access or an access-uplink port within a split horizon group will not be copied to other access and an access-uplink ports in the same split horizon group, but will be copied to an access-uplink ports in other split horizon groups.

Since split horizon is a per port feature in 7210 SAS, all SAPs associated with the port becomes part of split horizon group configured on that port.

Topology

The following figure shows an example of split horizon groups used to prevent communication between two access SAPs and between two access-uplink SAPs.

Figure 1. Split horizon group example

Using 7210 SAS-1 as an example:

  1. 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.

  2. 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.

  3. 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.

  4. 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.

Configuration guidelines

The following configuration guidelines must be followed to configure a split horizon group:

  1. Create a split horizon group in the config prompt. The group name must be unique across the system.

    7210-SAS1>config#info
#--------------------------------------------------
echo "Split-horizon-group Configuration"
#--------------------------------------------------
    split-horizon-group access create 
        description ‟Block access between access Ports”
    split-horizon-group access-uplink create
        description "Block access between access-uplink Ports"
    exit 
#-------------------------------------------------- 
7210-SAS1>config#

  2. Associate ports 1/1/4 and 1/1/5 with split horizon group ‟access” By default all ports are access ports. The default Ethernet encapsulation for access port is ‟null”.

    7210-SAS1>config#info
#--------------------------------------------------
echo "Port Configuration"
#--------------------------------------------------
    port 1/1/4
        split-horizon-group access
        ethernet
        exit
        no shutdown
exit 
    port 1/1/5
        split-horizon-group access
        ethernet
        exit
        no shutdown
  exit
#--------------------------------------------------


7210-SAS1>config#

  3. Configure ports 1/1/1 and 1/1/3 as access uplink and associate these ports with split horizon group ‟access-uplink” default Ethernet encapsulation for access uplink port is ‟qinq”.

    7210-SAS1>config# info
#--------------------------------------------------
echo "Port Configuration"
#--------------------------------------------------
    port 1/1/1
        split-horizon-group access-uplink
        ethernet
               mode access uplink
        exit
        no shutdown
exit 
    port 1/1/3
        split-horizon-group access-uplink
        ethernet
               mode access uplink
        exit
        no shutdown
  exit
#--------------------------------------------------


7210-SAS1>config#

  4. Create a VPLS instance 100.

    #--------------------------------------------------
echo "Service Configuration"
#--------------------------------------------------
    service
          customer 2 create
          exit
         vpls 100 customer 2 create
            stp
                shutdown
            exit
            sap 1/1/1:100.* create
            exit
            sap 1/1/3:100.* create
            exit
            sap 1/1/4 create
            exit
            sap 1/1/5 create
            exit
            no shutdown
    exit
...
#--------------------------------------------------
    Note:

    A split horizon on a port must be configured before creating any SAPs associated with that port.

Verification

The following shows the command usage to verify the split horizon configuration on a 7210 SAS.

7210-SAS1# show split-horizon-group 
===============================================================================
Port: Split Horizon Group
===============================================================================
Name                               Description                                 
-------------------------------------------------------------------------------
access                             Block access between access Ports           
                             
access-uplinkBlock access between access-uplink Ports   
             
No. of Split Horizon Groups: 2
===============================================================================
7210-SAS1#

The following shows the command usage to verify the port association with split horizon groups.

7210-SAS1# show split-horizon-group access 
===============================================================================
Port: Split Horizon Group
===============================================================================
Name                               Description                                 
-------------------------------------------------------------------------------
access                             Block access between access Ports                
-------------------------------------------------------------------------------
Associations
-------------------------------------------------------------------------------
Port1/1/4                          10/100/Gig Ethernet SFP                     
Port1/1/5                          10/100/Gig Ethernet SFP                     
 
Ports Associated : 2     
===============================================================================
7210-SAS1#


7210-SAS1# show split-horizon-group access-uplink 
===============================================================================
Port: Split Horizon Group
===============================================================================
Name                               Description                                 
-------------------------------------------------------------------------------
Access-uplink                      Block access between access-
uplink Ports                
-------------------------------------------------------------------------------
Associations
-------------------------------------------------------------------------------
Port1/1/1                          10/100/Gig Ethernet SFP                     
Port1/1/3                          10/100/Gig Ethernet SFP                     
 
Ports Associated : 2     
===============================================================================
7210-SAS1#