Applications
2.12
— Orbitor 6000 Installation & Applications Guide
Define a Variable Length IP Subnet Mask
The ISDN version of the Orbitor 6000 allows for the definition of subnet masks that
consist of all zeroes or all ones. Normally subnet masks of these types are not allowed.
The use of variable length subnets allows the creation of four distinct subnets with the use
of a two bit subnet size. A two bit subnet size under the standard configuration would
result in two useable subnets and two non-useable subnets. The non-useable subnets
would not be valid due to the fact that the subnet portion of the address would contain all
zeroes or all ones.
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 variable length subnet sizes from 1 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 variable length subnet
size of 1 will result in the creation of 2 sub-networks from the original IP network address.
So setting a subnet size of 1 will generate two resulting sub-networks with up to 126 host
addresses each. The new IP network addresses will be: 199.169.100.0 and
199.169.100.128. The subnet mask for the newly created networks will be
255.255.255.128.
1.
Nonstandard Subnets
Location:
Main
Configuration
Internet Set up
Nonstandard Subnets
To define a subnet mask that contains all zeroes or all ones, the
Nonstandard Subnets option must be set to enabled.
