HP-UX Reference (11i v1 00/12) - 1M System Administration Commands A-M (vol 3)

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ifconﬁg(1M) ifconﬁg(1M)

contiguous starting from the leftmost bit position in the 32-bit ﬁeld.

mask must contain at least the standard network portion, and the

subnet ﬁeld must be contiguous with the network portion. The sub-

net ﬁeld must contain at least 1 bit. For aggregating networks into

supernets, mask must only include a portion of the network part.

mask must contain contiguous 1’s in the bit positions starting from

the leftmost bit of the 32-bit ﬁeld.

arp Enable the user of the Address Resolution Protocol in mapping

between network level addresses and link level addresses (default).

If an interface already had the Address Resolution Protocol disabled,

the user must "unplumb" the interface before it can be enabled for

Address Resolution Protocol.

-arp Disable the use of the Address Resolution Protocol. If an interface

already had the Address Resolution Protocol enabled, the user must

"unplumb" the interface before it can be disabled for Address Resolu-

tion Protocol.

plumb Setup the Streams plumbing needed for TCP/IP for a primary inter-

face name. (See the Interface Naming subsection given below.). By

default, the plumb operation is done automatically when an IP

address is speciﬁed for an interface.

unplumb Tear down the Streams plumbing for a primary interface name. (See

the Interface Naming subsection given below.) Secondary interface

does not require "plumbing" and it can be removed by assigning an IP

address of 0.0.0.0.

Interface Naming

The interface name associated with a network card is composed of the name of the interface (e.g. lan

snap ), the ppa number which identiﬁes the card instance for this interface, and an optional IP index

number which allows the conﬁguration of multiple IP addresses for an interface. For LAN cards, the inter-

face name

lan will be used to designate Ethernet encapsulation and

snap for IEEE 802.3 encapsulation.

The

lanscan command can be used to display the interface name and ppa number of each interface that

is associated with a network card (see lanscan(1M)).

Multiple IP addresses assigned to the same interface may be in different subnets. An example of an inter-

face name without an IP index number is

lan0. An example of an interface name with a IP index number

lan0:1. Note: specifying lan0:0 is equivalent to lan0.

Loopback Interface

The loopback interface (lo0) is automatically conﬁgured when the system boots with the TCP/IP software.

The default IP address and netmask of the loopback interface are 127.0.0.1 and 255.0.0.0, respectively. The

user is not permitted to change the address of the primary loopback interface (lo0:0). It is permissible to

assign other IP addresses to lo0 with non-zero IP index numbers (lo0:1, lo0:2, etc). This allows a system to

have a "system IP" address that is availableas long as one interface remains usable.

Supernets

A supernet is a collection of smaller networks. Supernetting is a technique of using the netmask to aggre-

gate a collection of smaller networks into a supernet.

This technique is particularly useful when the limit of 254 hosts per class C network is too restrictive. In

those situations a netmask containing only a portion of the network part may be applied to the hosts in

these networks to form a supernet. This supernet netmask should be applied to those interfaces that con-

nect to the supernet using the ifconﬁg command. For example, a host can conﬁgure its interface to connect

to a class C supernet, 192.6, by conﬁguring an IP address of 192.6.1.1 and a netmask of 255.255.0.0 to its

interface.

DIAGNOSTICS

Messages indicate if the speciﬁed interface does not exist, the requested address is unknown, or the user is

not privileged and tried to alter an interface’s conﬁguration.

Section 1M−−338 − 2 − HP-UX Release 11i: December 2000

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