# 255.255.255.0 versus 255.255.252.0 - TCP-IP

This is a discussion on 255.255.255.0 versus 255.255.252.0 - TCP-IP ; Gurus, Say run a small internal network on the 172.16.x.x range. Typically, you would run with a 255.255.255.0 subnet masks to get you 254 hosts on this subnet. Now, say I mask at 255.255.252.0. Does this now mean I can ...

1. ## 255.255.255.0 versus 255.255.252.0

Gurus,

Say run a small internal network on the 172.16.x.x range. Typically, you
would run with a 255.255.255.0 subnet masks to get you 254 hosts on this
subnet. Now, say I mask at 255.255.252.0. Does this now mean I can get 512
hosts on the subnet?

--
Spin

2. ## Re: 255.255.255.0 versus 255.255.252.0

Spin wrote:
> Gurus,
>
> Say run a small internal network on the 172.16.x.x range. Typically,
> you would run with a 255.255.255.0 subnet masks to get you 254 hosts on
> this subnet. Now, say I mask at 255.255.252.0. Does this now mean I
> can get 512 hosts on the subnet?
>

It means you get 1022 hosts on each subnet.

Here's a way to work it out for yourself:

Equation from Binary:
2^ remaining host bits – 2 = Hosts per Subnet

Example: There are still 14 host bits remaining; 2^14 - 2 = 16382

Equation from CIDR:
2^ (32-CIDR) - 2 = Hosts per Subnet

Example: There are 14 host bits remaining: 2^ (32-18) - 2 = 16382 subnets

3. ## Re: 255.255.255.0 versus 255.255.252.0

On Aug 29, 11:56*am, "Spin" wrote:
> Gurus,
>
> Say run a small internal network on the 172.16.x.x range. *Typically, you
> would run with a 255.255.255.0 subnet masks to get you 254 hosts on this
> subnet. *Now, say I mask at 255.255.252.0. *Does this now mean I can get 512
> hosts on the subnet?
>
> --
> Spin

http://www.cisco.com/en/US/tech/tk36...80093f33.shtml

4. ## Re: 255.255.255.0 versus 255.255.252.0

Intuitive wrote:
> Spin wrote:
>> Gurus,
>>
>> Say run a small internal network on the 172.16.x.x range. Typically,
>> you would run with a 255.255.255.0 subnet masks to get you 254 hosts
>> on this subnet. Now, say I mask at 255.255.252.0. Does this now mean
>> I can get 512 hosts on the subnet?
>>

>
> It means you get 1022 hosts on each subnet.
>
> Here's a way to work it out for yourself:
>
> Equation from Binary:
> 2^ remaining host bits – 2 = Hosts per Subnet
>
> Example: There are still 14 host bits remaining; 2^14 - 2 = 16382

A mask of 255.255.252.0 yields 10 host bits, not 14.

2^10 - 2 = 1022 hosts, as you've stated.

>
>
>
> Equation from CIDR:
> 2^ (32-CIDR) - 2 = Hosts per Subnet
>
> Example: There are 14 host bits remaining: 2^ (32-18) - 2 = 16382 subnets
>

Best Regards,