255.255.255.0 versus 255.255.252.0

[Spin]

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

[Intuitive]

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

[GArlington]

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f33.shtml

[News Reader]

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,
News Reader