Applications
2.10
— Orbitor 6000 Installation & Applications Guide
Define an IP Subnet Mask
An IP network may be divided into smaller portions by a process called sub-netting. If for
example, a small company wishes to connect to the Internet, they might be assigned a
single class C IP network address (199.169.100.0). This network address allows the
company to define up to 255 host addresses within their network. Their network will be
attached to the Internet with an IP router.
Now if this company adds another physical location, they might want to have an internal
router to route between the two or more IP networks. An IP router may be desirable
between the two IP networks to minimize traffic on the router connection. The original IP
network address may be sub-netted into two or more smaller IP networks consisting of a
smaller number of host addresses in each location. This allows each of the sites to be a
smaller IP network and to be routed together to allow inter-network communication.
The Orbitor 6000 allows standard subnet sizes from 2 to 22 bits of the host field. The
subnet size determines how many bits of the host field of the original IP network address
will be used for the creation of subnets. In this example, a subnet size of 2 will result in
the creation of 4 sub-networks from the original IP network address. Since two of the
resulting sub-network will have either all zeros or all ones as the subnet address, they are
invalid. So setting a subnet size of 2 will generate two resulting sub-networks with up to
62 host addresses each. The new IP network addresses will be: 199.169.100.64 and
199.169.100.128. The subnet mask for the newly created networks will be
255.255.255.192. For information on defining variable length subnet masks refer to the
next section.
Figure 2-3 Defining an IP Subnet Mask
