Q & A on One LAN or Many LANs on a Campus,

Q: I have a question about LANs. Are computers on a large university campus on one LAN or many LANs?

A: In general one LAN is incapable of supporting an entire large campus. As a general rule, each LAN is limited to an area approximaely the size of a single building. Indeed, mnay large unoversity buildings have more than one LAN. There are exceptions, of course, but you can use that as a guideline.

Q: Is it right that Ips with same mask are on a same LAN?

A: "Ips" is not a valid technical term. I assume you mean IP addresses (the 32-bit value assigned to a host on an internet). If so, the answer is "no". It's not the mask itself that determines whether two computers are on the same network, but whether the prefixes of the two addresses match. The mask simply tells where the prefix ends.. For example, the network in the Xinu lab here at Purdue and the main CS departmental network both use the same mask:

255.255.255.0

However, the prefixes differ in the third octet. Thus, two hosts on those two networks might have addresses:

128.10.2.1

and

128.10.3.1

When the mask is applied (logical and), the resulting prefixes are

128.10.2.0

and

128.10.3.0

which differ. However, the following two addresses are on the same network because when the mask is applied, both addresses have prefix 128.10.2.0

128.10.2.26

and

128.10.2.3