Installing and Administering LAN/9000 Software

Chapter 6 137

Network Addressing

Internet Addresses

NOTE Do not assign the host addresses 0.0.0 or 255.255.255 (Class A), 0.0 or

255.255 (Class B), or 0 or 255 (Class C) to any nodes; these addresses are

reserved.

IP Address for Loopback Interface (lo0)

The loopback interface (lo0) is automatically conﬁgured when the

system boots with the TCP/IP software. The loopback interface is really a

“pseudo-device,” since there is no hardware card associated with it. This

interface is created solely to facilitate sending IP datagrams to the IP

loopback address 127.0.0.1.

The default IP address and netmask of the loopback interface are

127.0.0.1 and 255.0.0.0, respectively. By default, the loopback interface

sets up routing entries so that packets for any 127.*.*.* address will loop

back to the local host. Any attempt to change the address of the initial

loopback interface (lo0:0) will fail.