User Guide

30 NetWare TCP/IP Administration Guide
NetWare TCP/IP Administration Guide
103-000151-001
August 30, 2001
Novell Confidential
Manual 99a38 July 17, 2001
Figure 11 A single IP network divided into two subnets
A subnet mask indicates how the host portion of the IP address is divided into
a subnet address and a local host portion. The network mask is a 32-bit number
with all ones for all network and subnet address portions, and all zeros for the
host field. With a Class B network portion of 129.47 and a 4-bit subnet
address, for instance, the subnet mask consists of 20 ones and 12 zeros. In
essence, a subnet mask locally extends the network address portion of an IP
address and reduces the host portion.
Table 2 on page 31 shows an example of a Class C subnet with an IP address
of 200.2.1.209. To create a subnet address, bits are taken from the local host
portion. As the size of the subnet mask increases, the number of hosts
decreases and the number of subnets increases.
129.47.128.254 129.47.128.253
129.47.129.1
129.47.128.1
129.47.192.1
129.47.193.1
129.47.192.253129.47.192.254
Router
Subnet Mask for Network Address
129.47.0.0:
255.255.240.0 or 0xFF.0xFF.0xF0.0x00
(11111111.11111111.11110000.00000000)
Subnet
Address: 192(1100)
All Other
Networks
Subnet
Address: 128(1000)