User guide

Unnumbered interfaces IP
4-5
iMG/RG Software Reference Manual (IPNetwork Functions)
4.1.5.2 Configuring unnumbered interfaces
Unnumbered interfaces are created using the following CLI command:
IP ADD INTERFACE <name> <ipaddress> 255.255.255.255
For example:
ip add interface myinterface 192.168.101.3 255.255.255.255
In this command:
• myinterface is the unnumbered interface name.
• 192.168.101.3 is the router id. The router ID must be set to the IP address of one of the router’s normal
interfaces. The main use of the router ID is as the source address for packets sent on an unnumbered inter-
face from local applications or routing protocols. Router IDs are described in RFC1812 Requirements for
IP v4 Routers.
• 255.255.255.255 is a special subnet mask that identifies an unnumbered interface and distinguishes it from
any other type of interface.
You must also add a route before your unnumbered interface can send packets.
4.1.5.3 Creating a route
Because an unnumbered interface does not have a local subnet associated with it, no packets can be routed to
an unnumbered interface until a route is added. Let us just consider how this is done.
Usually, for Ethernet interface, routes are added with a gateway to be used for a particular destination.
For example:
ip add route myroute 10.0.0.0 255.0.0.0 gateway 192.168.101.10
This means that all packets for the 10.0.0.0 subnet will be sent to the address 192.168.101.10 as their next hop.
The gateway must be reachable directly, so 192.168.101.10 must be on a subnet served by one of the local inter-
faces.
But, for point-to-point links, you can add a route through the interface, without specifying a gateway address,
for example:
ip add route myroute 10.0.0.0 255.0.0.0 interface myinterface
All packets for the specified destination will be sent via the unnumbered interface called myinterface. This type
of route can be used for all interfaces with point-to-point links, not just for unnumbered interfaces.
On devices of the type FIBER B/D/E, MODULAR and ADSL B/C routes can be disabled and
enabled.Unless explicitely set: routes are created and enabled.