R3303-HP HSR6800 Routers Layer 3 - IP Services Configuration Guide

Reply from 172.16.2.2: bytes=56 Sequence=4 ttl=255 time=26 ms

Reply from 172.16.2.2: bytes=56 Sequence=5 ttl=255 time=26 ms

--- 172.16.2.2 ping statistics ---

5 packet(s) transmitted

5 packet(s) received

0.00% packet loss

round-trip min/avg/max = 25/25/26 ms

The output shows that the router can communicate with the host on subnet 172.16.2.0/24.

# Ping a host on subnet 172.16.1.0/24 from a host on subnet 172.16.2.0/24 to verify the connectivity.

Host B can be successfully pinged from Host A.

Configuring IP unnumbered

Logically, to enable IP on an interface, you must assign this interface a unique IP address. Yet, you can

borrow an IP address already configured on one of other interfaces on your device instead. 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 either when available IP addresses are inadequate or

when an interface is brought up only for occasional use.

Configuration guidelines

Follow these guidelines when you configure IP unnumbered:

• Serial, dialer, POS, and ATM interfaces can borrow IP addresses from Layer 3 Ethernet interfaces or

other interfaces.

• Layer 3 Ethernet interfaces and loopback interfaces cannot borrow IP addresses of other interfaces,

but other interfaces can borrow IP addresses of these 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 IP addresses, only the primary IP address can be borrowed.

• The IP address of the borrowing interface varies with that of the borrowed interface. If an IP address

is configured for the borrowed interface, the IP address of the borrowing interface is the same as

that of the borrowed interface. If no IP address is configured for the borrowed interface, no IP

address is assigned to the borrowing interface.

Configuration prerequisites

Assign a primary IP address to the interface from which you want to borrow the IP address. Alternatively,

you can configure the interface to obtain one through DHCP or PPP address negotiation.

Configuration procedure

To configure IP unnumbered on an interface: