10. Appendix: Port-Based Split Horizon

This chapter provides Port-Based Split Horizon configuration information.

10.1. Overview

Note:

Port-based split horizon is supported on all 7210 SAS platforms as described in this document, except the 7210 SAS-Mxp.

The port-based split horizon feature can be used to disable local switching on the 77210 SAS. A loop-free topology can be achieved using split horizon on 7210 SAS switches.

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

10.1.1. Topology

Figure 94 shows an example of split horizon groups used to prevent communication between two access SAPs and between two network ports.

Figure 94:  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 “network” is created to prevent any communication between port 1/1/1 and port 1/1/3 (configured as a network port) within the same VPLS.
  3. VPLS 100 is created on 7210 SAS-1 with spoke-SDPs on network port 1/1/1 and 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 (for example, spoke-SDPs on these ports) that belong to split horizon group “network” will be switched to ports (for example, SAPs on these ports) that belong to split horizon group “access” and vice versa based on the FDB entries for VPLS 100.

10.2. Configuration Guidelines

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

Note:

When configuring split horizon on a port, it must be configured before creating any SAPs associated with the port.

  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 network create
            description "Block access between network Ports"
        exit 
    #-------------------------------------------------- 
    7210-SAS1>config#
  2. Configure ports 1/1/4 and 1/1/5 as access ports and associate these ports with split horizon group “access”.
    7210-SAS1>config#info
    #--------------------------------------------------
    echo "Port Configuration"
     
    #--------------------------------------------------
        port 1/1/4
            split-horizon-group access
            ethernet
                mode access 
                access
                exit
            exit
            no shutdown
        exit 
        port 1/1/5
            split-horizon-group access
            ethernet
                mode access 
                access
                exit
            exit
            no shutdown
         exit
    #--------------------------------------------------
    7210-SAS1>config#
  3. Configure ports 1/1/1 and 1/1/3 as network ports and associate these ports with split horizon group “network”. The default Ethernet encapsulation for network port is null.
    7210-SAS1>config# info
    #--------------------------------------------------
    echo "Port Configuration"
     
    #--------------------------------------------------
        port 1/1/1
            split-horizon-group network
            ethernet
            exit
            no shutdown
    exit 
        port 1/1/3
            split-horizon-group network
            ethernet
            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 1/1/4 create
                exit
                sap 1/1/5 create
                exit
                spoke-sdp 1:1 create
                exit
                spoke-sdp 2:1 create
                exit
             no shutdown
        exit
    ...
    #--------------------------------------------------

10.2.1. Verification

The following output verifies 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
network                            Block access between network 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 network
===============================================================================
Port: Split Horizon Group
===============================================================================
Name                               Description                                 
-------------------------------------------------------------------------------
network                           Block access between network Ports
-------------------------------------------------------------------------------
Associations
-------------------------------------------------------------------------------
Port1/1/1                          10/100/Gig Ethernet SFP                     
Port1/1/3                          10/100/Gig Ethernet SFP                     
 
Ports Associated : 2     
===============================================================================
7210-SAS1#