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Chapter 32
Configuring IP Unicast Routing
Configuring Split Horizon
Routers connected to broadcast-type IP networks and using distance-vector routing protocols normally
use the split-horizon mechanism to reduce the possibility of routing loops. Split horizon blocks
information about routes from being advertised by a router on any interface from which that information
originated. This feature can optimize communication among multiple routers, especially when links are
broken.
In general, Cisco does not recommend disabling split horizon unless you are certain that your application
Note
requires it to properly advertise routes.
Beginning in privileged EXEC mode, follow these steps to disable split horizon on the interface:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
no shutdown
Step 4
ip address ip-address subnet-mask
Step 5
no ip split-horizon
Step 6
end
Step 7
show ip interface interface-id
Step 8
copy running-config startup-config
To enable the split horizon mechanism, use the ip split-horizon interface configuration command.
Configuring OSPF
This section briefly describes how to configure Open Shortest Path First (OSPF). For a complete
description of the OSPF commands, see the "OSPF Commands" chapter of the Cisco IOS IP Command
Reference, Volume 2 of 3: Routing Protocols, Release 12.2.
OSPF classifies different media into broadcast, nonbroadcast, and point-to-point networks. The switch
Note
supports broadcast and point-to-point networks (Ethernet interfaces configured as point-to-point links).
OSPF is an Interior Gateway Protocol (IGP) designed expressly for IP networks, supporting IP
subnetting and tagging of externally derived routing information. OSPF also allows packet
authentication and uses IP multicast when sending and receiving packets. The Cisco implementation
supports RFC 1253, OSPF management information base (MIB).
78-17058-01
Purpose
Enter global configuration mode.
Enter interface configuration mode, and specify the interface to
configure.
Enable the interface if necessary. By default, UNIs are disabled and
NNIs are enabled.
Configure the IP address and IP subnet.
Disable split horizon on the interface.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring OSPF
32-23
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Troubleshooting
