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IPX Networking Fundamentals

475

is an administrator-assigned address of four octets. This address is combined
with the MAC layer address of the node, creating a ten-octet address. This
system greatly reduces the administrative overhead at the network node--
workstation, printer, or other device. In addition, the addressing scheme is
independent of the IP subnet mask concept, and any number of nodes can
belong to an IPX network within the constraints of the medium and the
broadcast limitations of IPX itself.

As with TCP/IP addresses, IPX addresses can be written in several

formats. Most often, they're written in hexadecimal--for example,

00007C80.0000.8609.33E9

. The first eight hex digits (

00007C80

) rep-

resent the network portion of the address; the remaining 12 hex digits
(

0000.8609.33E9

) represent the node portion and are the MAC address of

the workstation. When referring to the IPX network, it's a common IPX cus-
tom to drop leading 0s. Thus, the above network address is referred to as IPX
network 7C80. The node portion is commonly divided into three sections of
four hex digits that are divided by periods, as shown.

Many networks use both IP and IPX concurrently. A common convention is to

use the IP decimal or hex values to make up the IPX network number; thus,

10.11.10.0

becomes IPX network 10d11d10 or 10d0Bd10 (the "d" is for

"dot"). Some network administrators alter this convention in favor of a frame

typelocation-segment format. For example, F4150001 could refer to the first

IPX network using the Ethernet II frame type in the San Francisco office (area

code 415). Please note that IPX network numbers must be unique within the

entire internetwork.

IPX simplifies functions for the network and server administrators, in that the

IP functions of DHCP, ARP, and DNS/WINS are included in the base function-
ality of the protocol. ARP packets are unnecessary because the MAC address is
part of the overall network address. Address assignment (the DHCP function in
IP) is also handled by IPX because all MAC addresses are unique, by design. The
network number is presumed unique as a function of both the internetwork
design and the administrator's policies. Finally, name resolution is a function of
the SAP (service advertising protocol) process, which automatically updates all
resources with the address and socket of all services. This simplification is not
without its penalties, because IPX and its higher-level protocol SPX have a rep-
utation for being chattier than TCP/IP.

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