subnetting number of hosts etc...

liven

Ok I am really getting the hang of the subnetting thing. But I am still getting hung up on one area,

the kind of question where given an IP, then give the mask, the question is: what ips will be in each of the subnets

I don't really have a good example, and I hope I am explaining myself in an understandable fashion. I am posting this because I do understand how this works, but it just takes me time to write it all out. I posted a similar question in regards to subnetting and got lots of great tips and tricks. So hopefully the same thing will happen here.

Basically I need a trick for this: given an IP, and its subnet. WHat are all the ip ranges of the other subnets? What is a quick way to figure this out?

bighornsheep

Let's say 192.168.1.35 / 27, find the range of valid hosts

Figure out your subnet mask, 255.255.255.224, now figure the block size, octet of significance is the fourth one, so 224, take that away from 256, answer is 32. So block size of 32. The subnet IDs are
192.168.1.0, .32, .64 etc...
.35 must be in the network ID .32, the valid IPs are from .32 through the next subnet - 1, so .32 through .63, the first and last IP can't be used, first is the subnet ID, last is the broadcast IP, so the valid hosts are .33 through .62

Is this what you mean?

liven

ya pretty much,

thanks

Just looking for a way to do this kind of question as quickly as possible.

This does help,

so thanks again.

networker050184

Bighornsheep's way is the same way I do it. I don't think there is any faster way. If there is I'd like to know too

bighornsheep

There are two faster ways actually,

1) memorize it, there's only a finite number of possibilities for subnetting
2) guess it!




not that I would endorse either of the options above, but I guess that this is my way of saying, learn this darn subnetting, whatever way works for you, use it! and keep it with you! It will make you look good when you dont have to run to your ip subnet calculator when you're talking with someone important!

shednik

bighornsheep wrote:

Let's say 192.168.1.35 / 27, find the range of valid hosts

Figure out your subnet mask, 255.255.255.224, now figure the block size, octet of significance is the fourth one, so 224, take that away from 256, answer is 32. So block size of 32. The subnet IDs are
192.168.1.0, .32, .64 etc...
.35 must be in the network ID .32, the valid IPs are from .32 through the next subnet - 1, so .32 through .63, the first and last IP can't be used, first is the subnet ID, last is the broadcast IP, so the valid hosts are .33 through .62

Is this what you mean?

Another way that test out taught me was rather than take 224 - 256 to get the block size is to take the last bit in binary that's a 1....for example in this one 255.255.255.11100000 the last bit thats a 1 is 32. for me thats been my method and it has helped me figure things out a little faster. just my 2 cents

gabrielbtoledo

shednik wrote:

bighornsheep wrote:

Let's say 192.168.1.35 / 27, find the range of valid hosts

Figure out your subnet mask, 255.255.255.224, now figure the block size, octet of significance is the fourth one, so 224, take that away from 256, answer is 32. So block size of 32. The subnet IDs are
192.168.1.0, .32, .64 etc...
.35 must be in the network ID .32, the valid IPs are from .32 through the next subnet - 1, so .32 through .63, the first and last IP can't be used, first is the subnet ID, last is the broadcast IP, so the valid hosts are .33 through .62

Is this what you mean?

Another way that test out taught me was rather than take 224 - 256 to get the block size is to take the last bit in binary that's a 1....for example in this one 255.255.255.11100000 the last bit thats a 1 is 32. for me thats been my method and it has helped me figure things out a little faster. just my 2 cents

Yes, I do this way too. It works for me. However I double check subtracting the subnet from 256.