Example for Configuring Split Horizon

This section describes how to configure split horizon to prevent routing loops.

Networking Requirements

In Figure 1, IPv6 addresses are assigned to all interfaces on each router; RIPng is configured on each router and RIPng services run normally. It is required that split horizon be configured on router A and router C.

Figure 1 Preventing routing loops

Interfaces 1 and 2 in this example are GE 0/1/0 and GE 0/1/8, respectively.

Configuration Notes

When configuring split horizon to prevent routing loops, note the following:

If both split horizon and poison reverse are configured, only poison reverse takes effect.

Configuration Roadmap

The configuration roadmap is as follows:

Enable split horizon.

Data Preparation

To complete the configuration, you need the following data:

RIPng network segments 2001:db8:3::1/96, 2001:db8:4::1/96, and 2001:db8:5::1/96 on Device A
RIPng network segments 2001:db8:1::2/64 and 2001:db8:2::2/64 on Device B
RIPng network segments 2001:db8:7::1/96, 2001:db8:8::1/96, and 2001:db8:9::1/96 on Device C
IPv6 addresses of each interface

Procedure

Configure split horizon.

Configure split horizon on the RIPng interfaces of all routers. The configurations of Device B and Device C are similar to the configuration of Device A. For configuration details, see Configuration Files in this section.

# Configure Device A.

[~DeviceA] interface gigabitethernet0/1/0
[~DeviceA-GigabitEthernet0/1/0] ripng split-horizon
[*DeviceA-GigabitEthernet0/1/0] quit
[*DeviceA] interface gigabitethernet0/1/1
[*DeviceA-GigabitEthernet0/1/1] ripng split-horizon
[*DeviceA-GigabitEthernet0/1/1] quit
[*DeviceA] interface gigabitethernet0/1/2
[*DeviceA-GigabitEthernet0/1/2] ripng split-horizon
[*DeviceA-GigabitEthernet0/1/2] quit
[*DeviceA] interface gigabitethernet0/1/3
[*DeviceA-GigabitEthernet0/1/3] ripng split-horizon
[*DeviceA-GigabitEthernet0/1/3] quit
[*DeviceA] commit

Verify the configuration.

# Run the display ripng 1 interface verbose command on Device A and Device C to check whether split horizon has been enabled. Use the command output on Device A as an example. If the displayed Split-Horizon field is Enabled, split horizon has been enabled.

[~DeviceA] display ripng 1 interface verbose
 GigabitEthernet0/1/0
    FE80::A0A:200:1
    State : UP, Protocol : RIPNG, MTU : 1440
    Metricin : 0 , Metricout : 1
    Default Route : Disabled
    Poison Reverse : Disabled
    Split Horizon : Enabled  
 GigabitEthernet0/1/1(10.1.1.1)
    FE80::A0A:200:1
    State : UP, Protocol : RIPNG, MTU : 1440
    Metricin : 0 , Metricout : 1
    Default Route : Disabled
    Poison Reverse : Disabled
    Split Horizon : Enabled  
 GigabitEthernet0/1/2
    FE80::A0A:200:1
    State : UP, Protocol : RIPNG, MTU : 1440
    Metricin : 0 , Metricout : 1
    Default Route : Disabled
    Poison Reverse : Disabled
    Split Horizon : Enabled  
 GigabitEthernet0/1/3
    FE80::A0A:200:1
    State : UP, Protocol : RIPNG, MTU : 1440
    Metricin : 0 , Metricout : 1
    Default Route : Disabled
    Poison Reverse : Disabled
    Split Horizon : Enabled

Configuration Files

Device A configuration file

#
sysname DeviceA
#
interface GigabitEthernet0/1/0
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:1::1/64
 ripng 1 enable
#
interface GigabitEthernet0/1/1
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:3::1/96
 ripng 1 enable
#
interface GigabitEthernet0/1/2
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:4::1/96
 ripng 1 enable
#
interface GigabitEthernet0/1/3
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:5::1/96
 ripng 1 enable
#
ripng 1
#
return

Device B configuration file

#
sysname DeviceB
#
interface GigabitEthernet0/1/0
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:1::2/64
 ripng 1 enable
#
interface GigabitEthernet0/1/8
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:2::2/64
 ripng 1 enable
#
ripng 1
#
return

Device C configuration file

#
 sysname DeviceC
#
interface GigabitEthernet0/1/0
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:2::1/64
 ripng 1 enable
#
interface GigabitEthernet0/1/1
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:7::1/96
 ripng 1 enable
#
interface GigabitEthernet0/1/2
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:8::1/96
 ripng 1 enable
#
interface GigabitEthernet0/1/3
 undo shutdown
 ipv6 enable
 ipv6 address 2001:db8:9::1/96
 ripng 1 enable
#
ripng 1
#
return