Configuring The Ethernet Interface As An Unnumbered; Interface - HP ProCurve 7000dl Series Basic Management And Configuration Manual

Configuring Ethernet Interfaces
Ethernet Interfaces
3-10

Configuring the Ethernet Interface as an Unnumbered

Interface

To conserve IP addresses on your network, you may want to create the
Ethernet interface as an unnumbered interface. When you assign the Ethernet
interface an IP address, that IP address cannot overlap with the IP addresses
assigned to other interfaces on the router. As a result, each interface on the
router that has an IP address represents an entire subnet. Depending on the
subnetting scheme you use, this could use more IP addresses than you
can spare.
You can configure the Ethernet interface (and other interfaces on the
ProCurve Secure Router) as an unnumbered interface. The Ethernet interface
will then use the IP address of the interface you specify. The Secure Router
OS uses the IP address of the specified interface when sending route updates
over the unnumbered interface.
Before configuring the Ethernet interface as an unnumbered interface, you
should be aware of a potential disadvantage: if the interface to which the IP
address is actually assigned goes down, the Ethernet interface will be unavail-
able. For example, suppose you configure the Ethernet 0/1 interface as an
unnumbered interface that takes its IP address from the Frame Relay 1.16
subinterface. If the Frame Relay 1.16 subinterface goes down, the Ethernet
0/1 interface will be unavailable as well.
To minimize the chances of the interface with the IP address going down, you
can assign the IP address to a loopback interface, which typically does not
go down.
To configure an Ethernet interface as an unnumbered interface, enter the
following command from the Ethernet interface configuration mode context:
Syntax: ip unnumbered <interface>
Valid interfaces include:
Asynchronous Transfer Mode (ATM) subinterfaces
the other Ethernet interface or Ethernet subinterfaces
demand interfaces
Frame Relay subinterfaces
High-level Data Link Control (HDLC) interfaces
loopback interfaces
PPP interfaces