46 CHAPTER 2: INSTALLING THE W EBCACHESubnets and Using aSubnet MaskYou can divide your IP network into sub-networks also known as subnets.Support for subnets is important because the number of bits assigned tothe device part of an IP address limits the number of devices that may beaddressed on any given network. For example, a Class C address isrestricted to 254 devices.If you have a small network (less than 254 devices), you may decide notto have multiple subnets.A subnet mask is used to divide the device part of the IP address into twofurther 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 thecorresponding bit in the IP address as part of the original networknumber or as part of the subnet number. These bits in the mask are set to0 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 youcontact your network administrator.Default Router A Router is a device on your network which is used to forward IP packetsto a remote destination. An alternative name for a Router is a Gateway.“Remote” refers to a destination device that is not directly attached tothe same network segment as the source device.The source device cannot send IP packets directly to the destinationdevice because it is in a different network segment. Instead you configureit to send the packets to a router which is attached to multiple segments.When it receives the IP packets, the router determines the next networkhop on the path to the remote destination, and sends the packets to thathop. This could either be the remote destination or another router closertowards the destination.This hop-by-hop process continues until the IP packets reach the remotedestination.To configure the Webcache, enter the IP address of the default router onthe local subnet in which the Webcache is located. If no default router
