Just passed my first CCNA semester but still haven't got a clue re sub net's. How many host's and how many bit's borrowed etc. Can anyone explain it in a easy fool proof way. Many thanks.

This link really helped me out.

http://www.ralphb.net/IPSubnet/

Basically what subnets do is split networks up into "sections" or smaller networks for managability and ease of use.

yeh thanks

you must know binary, period

here is the deal an ipaddress and a subnet mask is really a series of 4 bytes

10.0.0.1/255.0.0.0 = 00001010.00000000.00000000.00000000/11111111.000000000.00000000.00000000

line them up one on top of the other like so (slightly abreviated)

00001010.0.0.0
11111111.0.0.0

and all the combinations that line up with zeros in the mask are valid addresses for that network
add a bit to the mask and you get something like

00001010.00000000.0.0
11111111.10000000.0.0

which is to say that 00001010.00000000.0.0 - 00001010.01111111.11111111.11111111 are valid for that network, there are two caveats now [network address][host address] is the notation I will use,
[network address][all zeros] is the "network address" you can't give it to a host because it represents the entire network and [network address][all ones] is also off limits for hosts because it is the broacast address or all hosts, so if you are specifing a network to route to you use net network address if you want to ping all hosts you ping the broacast address

just a cisco note here, ip-noclass (if I remember the parameter name correctly) enables you to use arbitrary masks as opposed to the implied mask from the first octect of the address, i.e. 10.*.*.* is assumed to be a class A network

The original post is 8 months old, but nice explanation ikkyu

Cheers mate, and welcome to GSO!

8 months, hehe, how did he manage to even find it,

Welcome to GSO, hehe

Regards,
LiquidSilver.

that was like one of Jay's first posts lololol i remember that.

just looking for places to offer something somewhat usefull, didn't look at the date, only 42 more posts before I am a real person

Hehe, okay

8 month's time flys when your having fun. How things have changed

I like this web based tool : IP Calculator

hmm wow.. im jus startin this subnettin stuff in my comp engineerin class thx

Genius has subnetting functions.. az well az aatoolz..