46 CHAPTER 2: INSTALLING THE WEBCACHE
Subnets and Using a
Subnet Mask
You can divide your IP network into sub-networks also known as subnets.
Support for subnets is important because the number of bits assigned to
the device part of an IP address limits the number of devices that may be
addressed on any given network. For example, a Class C address is
restricted to 254 devices.
If you have a small network (less than 254 devices), you may decide not
to have multiple subnets.
A subnet mask is used to divide the device part of the IP address into two
further parts:
■ The first part identifies the subnet number.
■ The second part identifies the device on that subnet.
The bits of the subnet mask are set to 1 if the device is to treat the
corresponding bit in the IP address as part of the original network
number or as part of the subnet number. These bits in the mask are set to
0 if the device is to treat the bit as part of the device number.
If you are unsure about what mask to use, 3Com suggest that you
contact your network administrator.
Default Router A Router is a device on your network which is used to forward IP packets
to a remote destination. An alternative name for a Router is a Gateway.
“Remote” refers to a destination device that is not directly attached to
the same network segment as the source device.
The source device cannot send IP packets directly to the destination
device because it is in a different network segment. Instead you configure
it to send the packets to a router which is attached to multiple segments.
When it receives the IP packets, the router determines the next network
hop on the path to the remote destination, and sends the packets to that
hop. This could either be the remote destination or another router closer
towards the destination.
This hop-by-hop process continues until the IP packets reach the remote
destination.
To configure the Webcache, enter the IP address of the default router on
the local subnet in which the Webcache is located. If no default router
