Technical data

3.3.1 Multihomed Computers
Individual host computers can have multiple network interface cards per computer.
Such a computer is called multihomed. These physical interfaces can be connected
to different types of networks, such as Ethernet, FDDI, Token Ring, asynchronous
transfer mode (ATM), Gigabit Ethernet, and serial communications lines. Each
physical interface is associated with one device driver (network interface). A single
network interface can have more than one IP address.
_________________________ Note _________________________
If a host has multiple interfaces under DHCP (Dynamic Host
Configuration Protocol) control and receives a different host name
from a DHCP server on each of the DHCP-controlled interfaces, the
DHCP client uses the host name it receives on the primary interface
to configure the host name for the client. For more information about
DHCP, see Chapter 5.
3.3.2 Primary Interface
Although you can have multiple physical interfaces on a single computer, some of
the parameters that are configurable by DHCP are interface specific. Examples
of interface-specific parameters are the IP address and subnet mask. However,
most DHCP configurable parameters are systemwide configurable parameters.
Examples of systemwide parameters are the host name and DNS domain name.
The TCP/IP Services DHCP client supports controlled configuration of systemwide
configurable items by designation of a primary interface.
The primary interface is the interface on which the DHCP client uses systemwide
parameters received from the DHCP server to configure the system. Systemwide
parameters received on an interface that is not designated as primary are not
configured on your system by the server. Although only one interface on a system
is designated as the primary DHCP interface, the system is not required to have
any interface designated as primary.
If a system has multiple interfaces and only one is under DHCP control, you can
configure the systemwide parameters manually. DHCP client uses the following
rules to resolve conflicts:
• The only-one-primary-interface rule
This rule solves the potential conflict between two DHCP controlled interfaces
on a host getting different systemwide parameter values. To resolve the conflict,
you designate one interface to be the primary interface and the parameters that
you receive on that interface are the values the DHCP client uses to configure
the system. TCP/IP Services does not let you designate two primary interfaces.
• The primary-interface-not-required rule
This rule solves the problem of DHCP configuring interfaces with an IP address
but also keeping manual control of the systemwide parameters. In this case,
the DHCP client does not designate the interface as the primary interface, and
it ignores any systemwide parameters it receives from a DHCP server.
For details about configuring multiple interfaces, refer to the Compaq TCP/IP
Services for OpenVMS Management guide.
OpenVMS Server and Network Configurations 3–5