ZyXEL Communications Prestige 100, User Manual

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TCP/IP Configuration 69
TCP/IP Configuration
This chapter shows you how to configure the Prestige for TCP/IP.
Depending on your particular applications, you will need to
configure different menus. For instance, Internet access is the most
common application of TCP/IP. For this application, you should
configure Menu 4. We will illustrate the configuration for other
applications in the following sections.
IP Subnet Mask
A subnet mask is a 32-bit quantity that, when logically ANDed
with an IP address, yields the network number. For instance, the
subnet masks for class A, B and C without subnetting are
255.0.0.0, 255.255.0.0 and 255.255.255.0, respectively.
To create more network numbers, you shift some bits from the host
ID to the network ID. For instance, to partition a class C network
number 192.68.135.0 into two, you shift 1 bit from the host ID to
the network ID. Thus the new subnet mask will be
255.255.255.128; the first subnet will have network number
192.68.135.0 with hosts 192.68.135.1 to 129.68.135.126 and the
second subnet will have network number 192.68.135.128 with
hosts 192.68.135.129 to 192.68.135.254.
It is recommended that you use the same subnet mask for all
physical networks that share an IP network number. The table
below lists the additional subnet mask bits in dot decimal notations.
To use to following table, write down the original subnet mask and
substitute the higher order 0’s with the dot decimal of the
additional subnet bits. For instance, to partition your class C