Learn subnetting at http://easysubnet.com

$3.99 for an e-book with stuff you can find for free on the web (it could be worth it to save you the searching). Sample contents list shows lots of obsolete stuff about classful networking - NOT a good plan to learn that.

First sample question it gave me was:

Question: How many subnets and hosts can you get from the network 133.117.0.0 255.255.255.0?

The correct answer to that is between 1 subnet with 254 hosts and 64 subnets with 2 hosts. The answer given was:

Answer: 256 subnets and 254 hosts

Which is wrong. That's the answer to the question "How many subnets with mask 255.255.255.0 can you get from a network with mask

255.255.0.0, and how many hosts are on each?" or "How many /24 subnets can you get from a /16 prefix, and how many available host addresses are there in a /24 prefix?".

Sam

Yes indeed - that's some of the free stuff!

(3Com used to have a very good short description of subnet masking but I lost track of it - looks like they've expanded their offering.)

Sam