Installing and Administering LAN/9000 Software

172 Chapter7
LAN Device and Interface Terminology
Interfaces
Interfaces
HP-UX 11i allows you to configure multiple IP addresses for a single
physical interface. This allows a single system to be seen as multiple
systems, with multiple IP addresses and host names, even if the system
has only one physical interface card. The IP addresses assigned to a card
can generally be on the same subnet or on different subnets.
Logical interfaces are also used when an interface card is used for both
IP/Ethernet and IP/IEEE802.3 packets. (In HP-UX 11i, all IP packets
sent over IEEE802.3 must use Sub-Network Access Protocol (SNAP)
encapsulation.) Sending IP packets using Ethernet and sending IP
packets using IEEE 802.3 over the same card requires two separate
logical interfaces. To send IP packets using Ethernet and IEEE 802.3,
you must configure two logical interfaces, with two different IP
addresses. In addition, the IP addresses must be in two different
subnets. For logical interfaces with the same encapsulation, the IP
addresses can be on the same or on different subnets.
In HP-UX 11i, the interface names used for ifconfig and
/etc/rc.config.d/netconf statements can have a logical interface
number appended to the card name. The syntax is:
nameX [: logical_interface_number ]
name is the class of the interface. Valid names include lan (Ethernet
LAN, Token Ring, FDDI, or Fibre Channel links), snap (IEEE802.3 with
SNAP encapsulation), atm (ATM), du (Dial-up), ixe(X.25), or mfe (Frame
Relay).
X is the Physical Point of Attachment (PPA). This is a numerical index
for the physical card in its class. For LAN devices, the lanscan command
displays the concatenated name and PPA number in the “Net-Interface
NamePPA” field.
logical_interface_number is an index that corresponds to the logical
interface for the specified card. The default is 0. The interface name lan0
is equivalent to lan0:0, lan1 is equivalent to lan1:0, and so on.
The first logical interface for a card type and interface is known as the
initial interface. You must configure the initial interface for a
card/encapsulation type before you can configure subsequent interfaces
for the same card/encapsulation type. For example, you must configure
lan2:0 (or lan2) before configuring lan2:1. Once you have configured the