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Managing IP Interfaces
You can manage IP interfaces with the following tasks:
- Setting Up an Unnumbered Interface
- Adding a Host Route to a Peer on a PPP Interface
- Shutting Down an IP Interface
- Removing an IP Configuration
- Clearing IP Interface Counters
- Disabling the Forwarding of IP Packets on an SRP Ethernet Interface
- Forcing an IP Interface to Appear Up
- Adding a Description to an IP Interface or Sub-Interface
- Enabling SNMP Link Status Traps on an IP Interface
- Configuring the Speed of an IP Interface
Setting Up an Unnumbered Interface
An unnumbered interface does not have an IP address assigned to it. Unnumbered interfaces are often used in point-to-point connections where an IP address is not required.
You can set up an unnumbered interface using the ip unnumbered command. This command enables IP processing on an interface without assigning an explicit IP address to the interface.
You can supply an interface location, which is the type and number of another interface on which the router has an assigned IP address. This interface cannot be another unnumbered interface.
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To set up an unnumbered interface:
- Issue the ip unnumbered command
in Interface Configuration mode.host1(config-if)#ip unnumbered fastEthernet 0/0
Use the no version to disable IP processing on an interface.
Adding a Host Route to a Peer on a PPP Interface
You can enable the ability to create host access routes on a Point-to-Point Protocol (PPP) interface using the ip access-routes command. This feature is useful in B-RAS applications.
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To enable the ability to create host access routes on the PPP interface:
- Issue the ip access-routes command
in Interface Configuration mode.host1(config-if)#ip access-routes
Use the no version to disable this feature.
Shutting Down an IP Interface
You can disable an interface to the router at the IP level without removing it using the ip shutdown command.
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To disable an IP interface:
- Issue the ip shutdown command
in Interface Configuration mode.host1(config-if)#ip shutdown
Use the no version to restart the interface.
Removing an IP Configuration
You can remove the IP configuration from an interface or subinterface using the no ip interface command.
To remove the IP configuration from an interface and disable IP processing on the interface:
- Issue the no ip interface command
in Interface Configuration mode.host1(config-if)#no ip interface
Clearing IP Interface Counters
You can clear the counters on one or more specified IP interfaces using the clear ip interface command.
To clear counters on a specified IP interface:
- Issue the clear ip interface command in Privileged Exec mode.host1#clear ip interface pos 2/0
Disabling the Forwarding of IP Packets on an SRP Ethernet Interface
You can disable forwarding of packets on an switch route processor (SRP) Ethernet interface using the ip disable-forwarding command.
The purpose of this command is to maintain router performance by maximizing the CPU time available for routing protocols. Although you can allow data forwarding on the SRP Ethernet interface, router performance will be affected.
You see an error message if you try to set this command for interfaces other than the SRP Ethernet interface.
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To disable forwarding of packets on the SRP Ethernet interface:
- Issue the ip disable-forwarding command in Interface Configuration mode.host1(config-if)#ip disable-forwarding
Use the no version to enable forwarding of packets on the interface.
Forcing an IP Interface to Appear Up
You can force an IP interface to appear as if it is up using the ip alwaysup command, regardless of the state of the lower layers.
This command reduces route topology changes when the network attached to this link is single-homed.
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To force an IP interface to appear as up regardless of the state of lower layers:
- Issue the ip alwaysup command
in Interface Configuration mode.host1(config-if)#ip alwaysup
Use the no version to make the interface appear in the current state.
Adding a Description to an IP Interface or Sub-Interface
You can add a text description or an alias to a static IP interface or subinterface. Adding a description helps you identify the interface and keep track of interface connections. The description or alias can be a maximum of 256 characters. If no IP interface currently exists, then a static IP interface is automatically created on the current layer 2 interface and the description is applied to that static IP interface. You cannot assign a profile to a layer 2 interface that has a static interface configured above it.
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To assign a text description or an alias to an IP interface:
- Issue the ip description command
in Interface Configuration mode.host1(config-if)#ip description canada01 ip interface
Note: You can use this command in Subinterface Configuration mode.
Use the no version to remove the text description or alias.
Enabling SNMP Link Status Traps on an IP Interface
You can enable link status traps on an interface using the snmp trap ip link-status command.
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To enable link status traps on an interface:
- Issue the snmp trap ip link-status command in Interface Configuration mode.host1(config-if)#snmp trap ip link-status
Use the no version to disable link status traps on an interface.
Configuring the Speed of an IP Interface
You can set the speed of an IP interface using the ip speed command. By default, the speed is determined from a lower-layer interface.
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To set the speed of the interface in bits per second:
- Issue the ip speed command
in Interface Configuration mode.host1(config-if)#ip speed 1000
Use the no version to set the speed to the default, 0.
