14-4
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 14 Configuring IP Unnumbered Interface
Configuring IP Unnumbered Interface Support with DHCP Server
The option to add dhcp host routes as connected routes is available in Cisco IOS. When using
connected mode, however, the clear ip route * command deletes the DHCP host connected routes
permanently. To avoid this situation for a Layer 3 interface (SVI), enter shut and then no shut. To
enable IP unnumbered to use static routes, enter the ip dhcp route static command.
IP Redirect is not sent by an interface configured with IP Unnumbered Interface.
IP Unnumbered Interface is unable to forward multicast source packets.
Configuring IP Unnumbered Interface Support with DHCP Server
Note DHCP must be configured and operational.
This section contains the following procedures:
Configuring IP Unnumbered Interface Support on LAN and VLAN Interfaces, page 14-4
Configuring IP Unnumbered Interface Support on a Range of Ethernet VLANs, page 14-5

Configuring IP Unnumbered Interface Support on LAN and VLAN Interfaces

To configure IP unnumbered interface support on a single LAN or VLAN interface, perform this task.
In the following example, Ethernet VLAN 10 is configured as an IP unnumbered interfaces:
Switch> enable
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface vlan 10
Switch(config-if)# ip unnumbered Lookback 0
Command Purpose
Step 1 Switch# enable Enables privileged EXEC mode.
Enter your password if prompted.
Step 2 Switch# configure terminal Enters global configuration mode.
Step 3 Switch(config)# interface [fastethernet |
gigabitethernet | tengigabitethernet | vlan
vlan | port-channel | loopback]
Enters interface configuration mode and the interface to be
configured as a tunnel port.
Step 4 Switch(config-if)# ip unnumbered type number Enables IP processing on an interface without assigning an
explicit IP address to the interface.
The type and number arguments specify another interface
on which the switch has an assigned IP address. The
interface specified cannot be another unnumbered interface.
Step 5 Switch(config-if)# exit Returns to global configuration mode.
Step 6 Switch(config)# end Returns to privileged EXEC mode.
Step 7 Switch# show running-config Verifies that IP unnumbered support has been configured
correctly.