aguilera
07-16-2007, 09:39 AM
Why do we subnet?
So we can create multiple networks from one single network.
How do we subnet?
First you have to find out how many networks you want to create.
What helps determine this?
Well we ask ourselves….How many departments does our company have (A department, or group is the same as a subnet!)
If you have 10 dept. in a company, with 12 employees in each department, then you need 10 subnets.
If you are given network 192.168.10.0 / 24 this is only 1 Network and you need 10.
This is one big piece of wire that can hold up to 254 host on it… but that is not what we need. We need 10 different pieces of wire that can hold at least 12 hosts on them.
How many of those host bits will we need to convert to network bits in order to create the 10 networks?
To calculate this we use:2^ __ = 10
2^2=4 not enough
2^3=8 still not enough
2^4=16 This is it!
We need 4 host bits converted into network bits.
Our original mask was 255.255.255.0 or /24 which meant we have 24 network bits.
Our new mask will take 4 of those oringal 8 host bits and convert them to network bits.
Our new mask will be 255.255.255.240 or /28 which means we now have 28 network bits. You get it? First we had /24, then we added 4 network bits now we have /28.
Do we still have enough host bits to accomondate those 12 employees?
Our original mask was 255.255.255.0 or /24 which meant we have 24 network bits and 8 Host bits (2^8= 256 - 2=254 host per network). Our new mask will take 4 of those oringal 8 host bits and convert them to network bits.This means we now only have 4 Host bits left.
Can we still support 12 employees on each of the new subnets? (2^4=16 - 2 = 14)
We sure can! Our job is done!
So we can create multiple networks from one single network.
How do we subnet?
First you have to find out how many networks you want to create.
What helps determine this?
Well we ask ourselves….How many departments does our company have (A department, or group is the same as a subnet!)
If you have 10 dept. in a company, with 12 employees in each department, then you need 10 subnets.
If you are given network 192.168.10.0 / 24 this is only 1 Network and you need 10.
This is one big piece of wire that can hold up to 254 host on it… but that is not what we need. We need 10 different pieces of wire that can hold at least 12 hosts on them.
How many of those host bits will we need to convert to network bits in order to create the 10 networks?
To calculate this we use:2^ __ = 10
2^2=4 not enough
2^3=8 still not enough
2^4=16 This is it!
We need 4 host bits converted into network bits.
Our original mask was 255.255.255.0 or /24 which meant we have 24 network bits.
Our new mask will take 4 of those oringal 8 host bits and convert them to network bits.
Our new mask will be 255.255.255.240 or /28 which means we now have 28 network bits. You get it? First we had /24, then we added 4 network bits now we have /28.
Do we still have enough host bits to accomondate those 12 employees?
Our original mask was 255.255.255.0 or /24 which meant we have 24 network bits and 8 Host bits (2^8= 256 - 2=254 host per network). Our new mask will take 4 of those oringal 8 host bits and convert them to network bits.This means we now only have 4 Host bits left.
Can we still support 12 employees on each of the new subnets? (2^4=16 - 2 = 14)
We sure can! Our job is done!