how many nodes can you have in subnet?

x_Danny_x

i forgot how to get the number, heck i forgot the formula for it

for example, how many nodes can you have in a 255.255.255.252 subnet???

mwgood

Take the last octect and subtract from 256, then subtract 2.

256-252=4
4-2=2 hosts

freak

Find out what the amount of host bits are via the subnet mask. Let's name it "n"

Now apply (2^n)-2 to find out how many *valid* hosts there are in that subnet.

Check out my free subnetting study guide at www.FreakNotes.com for more info. Let me know if I can help further

x_Danny_x

thanks for the help guys,

so subnetworks do have a broadcast and network adresses, i keep forgetting that. I thought you only do the subtraction of 2 on the Class A, B, C addresses.


so the last octec has to be a "1" or a "2" in binary cause those are the only 2 acceptable right ?

Drakonblayde

No.. if you're subnetting a class C, the last octet can only be 192, 224, 240, 248, or 252.

You have to leave at least two bits open for node addressing. If you only leave one bit, that means your only possible node address would be 1 or 2 which would be the subnet ID and the broadcast, leaving you no addresses for node hosting. If you leave 2 bits, you have 4 possibilities for addresses, two taken up by subnet ID and broadcast, leaving 2 available for host addressing.

crabeater

D-Blayde is right. Remember that those numbers (192, 224, etc) come form the adding of binary bits from highest to lowest in the octet, making these the only possible numbers for the mask.

This is also an easy way for beginners to get the Class A-B-C right.

00000000 0 start A
10000000 128 starts B (add 128
11000000 192 start C (add 64
11100000 224 D (add 32

see the progression? And as bits are taken for the network section, host can be figured using 'what would the next number be?', or use a 2's complement & add the binary placement values (2+4+8+...)-2

Class D & E have books saying different things for the ranges, but since they are not covered in the test, you can research them as needed (there SHOULD NOT be differences, but ....)

Hope I got all the stated clearly.

freak

There is a full, free study guide on subnetting at www.FreakNotes.com that could beneficial for you. I am also working on adding subnetting exercises in the coming week. I hope this helps

x_Danny_x

freak wrote:

There is a full, free study guide on subnetting at www.FreakNotes.com that could beneficial for you. I am also working on adding subnetting exercises in the coming week. I hope this helps

thanks guys! I am already certified in Network +, i have to learn this all over for the Microsoft and Cisco cause they just drilled me in one course with it!


Freak, your site wont let me logon as "guest", I'm I doing something wrong???????

freak

not sure, it seems to be working to me. Note that not all study guides are accessible as "guest". Some require for you to sign up - which is free. I can't remember if that is one of them...