Configuring IP unnumbered
About IP unnumbered
You can configure an interface to borrow an IP address from other interfaces. This is called IP unnumbered, and the interface borrowing the IP address is called IP unnumbered interface.
You can use IP unnumbered to save IP addresses when available IP addresses are inadequate or when an interface is used only occasionally.
Restrictions and guidelines
Loopback interfaces cannot borrow IP addresses of other interfaces, but other interfaces can borrow IP addresses of loopback interfaces.
An interface cannot borrow an IP address from an unnumbered interface.
Multiple interfaces can use the same unnumbered IP address.
If an interface has multiple manually configured IP addresses, only the manually configured primary IP address can be borrowed.
A dynamic routing protocol cannot be enabled on the interface where IP unnumbered is configured. To enable the interface to communicate with other devices, configure a static route to the peer device on the interface.
Prerequisites
Assign an IP address to the interface from which you want to borrow the IP address. Alternatively, you can configure the interface to obtain one through BOOTP, or DHCP.
Procedure
Enter system view.
system-view
Enter interface view.
interface interface-type interface-number
Specify the interface to borrow the IP address of the specified interface.
ip address unnumbered interface interface-type interface-number
By default, the interface does not borrow IP addresses from other interfaces.