Tcp/Ip Configuration; Ip Subnet Mask - Planet IRT-1001ST User Manual

TCP/IP Configuration

This chapter shows you how to configure your IRT-1001 or IRT-1002
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 networks 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 0s with the dot decimal of the additional subnet bits. For instance,
to partition your class C network 204.247.203.0 with subnet mask
255.255.255.0 into 16 subnets (4 bits), the new subnet mask becomes
255.255.255.240.
IRT-1000 series User's Guide
Number of Bits
1
Dot Decimal
128
63