Managing IP Interfaces

You can manage IP interfaces with the following tasks:

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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To set up an unnumbered 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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To enable the ability to create host access routes on the PPP interface:

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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To disable an IP 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:

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:

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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To disable forwarding of packets on the SRP Ethernet 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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To force an IP interface to appear as up regardless of the state of lower layers:

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.

Note:

  • The ip description command is replacing the description command to assign a description to a static IP interface.
  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To assign a text description or an alias to an IP interface:

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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To enable 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.

Note:

  • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
  • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

To set the speed of the interface in bits per second:

Related Documentation