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Prestige 128IMH User’s Guide ZyXEL
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Page 8-1
8. TCP/IP Configuration
This chapter shows you how to configure the Prestige for TCP/IP. Configure dufferent
menus for different applications. For instance, Internet access is the most common
application of TCP/IP. For this application, you should configure menu 4. We illustrate the
configuration for other applications in the following sections.
8.1. 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 192.168.1.0 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 192.168.1.1 to
129.168.1.126, and the second subnet will have network number 192.168.1.128 with hosts
192.168.1.129 to 192.168.1.254.
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 the 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 network 192.168.1.0 with subnet mask 255.255.255.0 into 16 subnets (4 bits),
the new subnet mask becomes 255.255.255.240.
Number of Bits Dot Decimal
1 128
2 192
3 224
4 240
5 248
6 252
7 254
8 255
Table 8-1 IP Sunnet Mask