Users Guide

Layer 3 Routing Commands 1510
Example
The following example enables IPv4 routing for VLAN 15
console(config)#vlan 15
console(config-vlan15)#interface vlan 15
console(config-if-vlan15)#ip address 10.0.3.2 /8
console(config-if-vlan15)#exit
console(config)#ip routing
ip unnumbered
This command is used to identify an interface as an unnumbered interface
and specify the numbered interface providing the borrowed address. The
numbered interface must be a loopback interface. To stop borrowing an
address, use the no form of the command.
Syntax
ip unnumbered loopback loopback-id
no ip unnumbered
• loopback-id—The loopback identifier (Range 0–7)
Default Configuration
The are no ip unnumbered interfaces by default.
Command Mode
Interface (VLAN) Configuration
User Guidelines
IP unnumbered interfaces are supported in the default VRF only.
The interface should be configured as able to borrow an IP address, i.e. a
routing interface with no IP address.
The loopback interface is the numbered interface providing the borrowed
address. The providing loopback interface cannot be unnumbered. The
loopback interface is identified by its loopback interface number.
It is a misconfiguration for two routers, R1 and R2, to be connected by a link
where R1’s interface is unnumbered and R2’s interface is numbered. If a
static route is configured on R2 using R1’s IP address as next hop, the static