22Configuration guidelinesFollow these guidelines when you configure IP unnumbered:• Layer 3 Ethernet interfaces and loopback interfaces cannot borrow IP addresses of other interfaces,but other interfaces can borrow IP addresses of these interfaces.• Synchronous and asynchronous serial interfaces, and dial-up interfaces can borrow IP addresses ofEthernet 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 primaryIP address can be borrowed.Configuration prerequisitesAssign an IP address to the interface from which you want to borrow the IP address. Alternatively, youcan configure the interface to obtain one through BOOTP, DHCP, or PPP address negotiation.Configuration procedureTo configure IP unnumbered on an interface:Step Command Remarks1. Enter system view. system-view N/A2. Enter interface view. interface interface-typeinterface-number N/A3. Specify the interface to borrow theIP address of the specifiedinterface.ip address unnumberedinterface interface-typeinterface-numberBy default, the interface does notborrow IP addresses from otherinterfaces.A dynamic routing protocol cannot be enabled on the interface where IP unnumbered is configured. Toenable the interface to communicate with other devices, configure a static route to the peer device on theinterface. For more configuration information, see "IP unnumbered configuration example."Displaying and maintaining IP addressingExecute display commands in any view.Task CommandDisplay IP configuration and statistics for the specifiedor all Layer 3 interfaces. display ip interface [ interface-type interface-number ]Display brief IP configuration information for thespecified or all Layer 3 interfaces.display ip interface [ interface-type[ interface-number ] ] brief
