IP and Subnets

KTM200 used Ask the Experts™
Hi all, i havent had to worry too much about subnets as the networks i work with are all smaller that 255 so a single subnet is sufficient so my IP routing is poor. However i do have a site with more that 255 and have them on which gives me more than enough IP's but i do have some questions. Being on this i apparently get 64 subnets, please could someone explain this in more detail, how would i use 64 subnets if i needed them and what would they look like

I would also appreciate if someone could recommend a web source to learn and understand IP, subnets etc... I have visited a few site but they are hard to follow and i cant seem to see it in real world applications as i dont get to practice on large networks

Thanks all
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David AtkinTechnical Director
Top Expert 2015


This is a good online calculator for working it out:

In your situation its more important to know that you would get 1022 hosts on this subnet.  Your useable addresses range would be -

This explains subnetting well:


Thanks Scorpeo, i did see that my DHCP scope gives me the 1022 hosts. Am i correct in saying that all these 1022 hosts will be able to communicate over the different segments e.g. will be able to communicate with
Yes, with the correct subnet mask ( or /22) set on all devices.  If you require routing between subnets, ensure all dvices have correct default gateway too...
Technical Director
Top Expert 2015
Yes that's correct. You can use all addresses in that range and they will be able to communicate with each other.

This explains it in a little more detail:
A "subnet" need not have but 256 addresses.  It can have fewer and it can have more.
So, what you have is a subnet with more: 1024.
One taken for "network" address
One taken for "broadcast" address
Leaves 1022.

The DHCP scope should *not* have 1022 addresses.  That's because at least the gateway should have a fixed address and probably does. And, with 1022 usable addresses total it means that the gateway address is inside the DHCP pool.  It might work but it's surely not good practice.  Then, usually, folks have printers, routers, managed switches that don't respond to DHCP and have to be set manually.  Their addresses should be outside the DHCP range as well.

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