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Class C IP address with Class B mask

By techinfo ·
Hi Guys,
I have an issue now to support a new IP schema for a network. This network is working on class C IP addresses,, and they plan for future where the number of clients will be more than 300 users, so they want to move to class B. My question is, what about using the same IP address range but with the subnet mask of class B, i.e. the IP scheme will be Is it OK to be used or not, and if it is not right to be used, what are the reasons for that and what are the bad results of using IP scheme like this ...
Thanks and Regards,

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Class B subnet masking in 192.168

by lgarvin In reply to Class C IP address with C ...

You could create one large Class B network in, but I don't think that's exactly what you want. You mention that you want "more than 300 users" per network. Aside from the various questions concerning physical layout about whether 300 hosts per network is a good idea, let me expand on how to do this with logical addressing.

Creating a subnet mask of instead of would give you 128 networks of 510 hosts. Creating a subnet mask of would give you 64 networks of 1022 hosts. If you wanted more hosts per logical IP network, you could create subnets with smaller bit lengths.

Now, having established that the addressing scheme can be done, the question still remains whether it's a "goodidea" to put 300 hosts on the same IP subnetwork. This is a function of what methodologies are used to join those networks together, and how the traffic among the 300+ hosts is segmented in collision domains.

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3COM IP Calculator

by chris.rodgers In reply to Class B subnet masking in ...

Just a note that 3COM has a pretty good IP calculator out there, it saves a lot of time. Again though it would also depend on the kind of network you wan't to build doing what you said will give you a pretty flat network, but should work fine.

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by chris.rodgers In reply to Class C IP address with C ...

That's what I do with my network. I use with and I have certain banks set aside for servers and DHCP and labs.

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