ZyXEL Communications Prestige 128L, User Manual

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TCP/IP Configuration 45
6
TCP/IP Configuration
This chapter shows you how to configure your 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 192.68.135.126 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 0s with the dot decimal of the additional subnet bits. For instance,