IP Question

I am doing an IP questionaire / test & have come to a halt on the following question

You have a network defined as 1.2.3.16/28, what are the range of usable addresses on that network & which addresses cannot be used for PCs & why

I have written out the question exactly as written

Thanks for all responses

/28 tells you that you have a subnetted network. you will need to write out all the subnets for this network....or use a subnet calc; cheater, lol. you can find the number of usable subnet by using this formula 2 ^ N - 2 = usable subnets (where N is the number of bits borrowed); read a book to find out why.

the /28 indicates that CIDR is being used to allocate the address - basically this is a method of allocating IPv4 addresses more efficiently. This allows for 16 hosts, although you have to subtract the network address (1.2.3.16) and the broadcast address (1.2.3.32) from this - hence the "-2" in the calculatin that csamuels gives.

For more info check out wikipedia: http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

Thanks for the info, will check out the link later on
It all appears as clear as mud at the moment !