Applications
2.14
— Orbitor 6000 Installation & Applications Guide
Define a Variable Length IP Subnet Mask While Using Static IP Routes
In addition to the ability to define variable length subnet sizes, the ISDN version of the
Orbitor 6000 also allows the IP routing protocol to be changed from RIP to none.
Changing the IP routing protocol to none allows the Orbitor to be used in configurations
where a routing protocol other than RIP is being used. The IP routing functions of the
Orbitor are accomplished through the use of static IP routes when the routing protocol is
set to none.
Another use of static routing only would be the uneven allocation of subnet sizes within the
network. A class C network for example may be divided up into 4 sub-networks by using
a two bit subnet mask. Two of the resulting sub-networks may be used for two remote
office LAN locations while the remaining two sub-networks may be combined to form a
larger local LAN at the central office. Static IP routes are then created between the
networks to allow for data transfer.
If for example, a 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 two other physical locations, they might want to have an
internal router to route between the internal IP networks. The original IP network address
will be sub-netted into three 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 at the central office and 2 at the two remote offices will result in the creation of 3
sub-networks from the original IP network address.
Setting a subnet size of 1 at the central office will allocate half of the available host
addresses resulting in up to 126 host addresses available. The new central office IP
network address will be: 199.169.100.0. The subnet mask for the newly created network
will be 255.255.255.128.
Setting a subnet size of 2 at the two remote offices will allocate one quarter of the
available host addresses resulting in up to 62 host addresses available at each of the two
remote offices. The new remote offices IP network addresses will be: 199.169.100.128
and 199.169.100.192. The subnet mask for the newly created remote office networks will
be 255.255.255.192.
The configuration options described here are only for initial set up and configuration
purposes. For more complete information on all of the configuration parameters
available please refer to the ISDN Menu Reference Manual file on the
accompanying disks.
