/23 subnetting question

A /23 has only 508 hosts total (255 * 2 = 510, minus network/broadcast addresses). With only a single /23, you can't service 520 hosts as you are asking. Second, and because networks can only be split into networks of specific sizes, you can't create networks for exactly that many hosts. You could do a /24 for the 200 requirement, or perhaps a /

A close suggestion: /24 = 255 hosts (10.20.0.0 255.255.255.0) /25 = 128 hosts (10.21.0.0 255.255.255.128 /26 = 64 hosts (10.21.128.0 255.255.255.192) /27 = 32 hosts (10.21.192.0 255.255.255.224) /27 = 32 hosts (10.21.224.0 255.255.255.224)

This would be as close as you can get without requiring more networks and/or more network space.......

And technically these are 2 addresses off each....for network/ broadcast addresses. So 254, 126, 62, etc.

i am only restricted to 10.20.x.x/23, only the third octet can be played around with can i use

I'm sorry, I was typing as a /15 above....not /23......same thing applies but I was 1 octet off............

So you can use any 10.20.x.x/23? I guess I didn't pick up on that before. Why can't you segment beyond /23 as proposed? You would easily meet your requirements by splitting up the /23 as I had suggested (slight modifications to meet your exact requirements, and using a small portion of the second /23 (10.20.2.0) for the last 120.

That would do you fine............