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Rgd: Subnetting about 370 hosts on a /24 Network

I am doing subnetting for the following.

There is a school, which got level 1 which is main lobby and 5 levels of classrooms ( level 2 to 6 )

I calculated that level 1 will use 161 hosts. Level 2-6 - each will use 55 hosts per level

So i was wondering how do i subnet it .

For the main IP address is 203.218.71.0/24

I was thinking to subnet 3/4 to Main Lobby - I can split the main lobby into 3 sections with about 60 hosts each section

I was thinking to subnet 1/4 to level 2-6 floor

Which then further subnet them by slicing into 2 slice ( 4 levels per slice ) Each slice will have about 60 hosts ( can settle 4 levels )

Total we will use 5 out of 8 slices ( 1/2 x 1/4 ) - 5 levels

But for the ip address, how do i do it, is my subnetting workable ?

My main purpose is to link the whole school and cover the internal network, which the one connect to the internet is the main router > which then distribute to the switch & access point and do the linking.

Thanks

Hope to see your comment & thanks for helping.

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    You can't fit more than 252 addresses into a /24 you'll need more addresses.
    – NickW
    Feb 20, 2013 at 10:08
  • @NickW in my case, given that i got the ip address 203.218.71.0/24 , how do i handle 370 hosts. i know i am given a router, and i can add more devices if i want.
    – user2017011
    Feb 20, 2013 at 10:10
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    NAT, or IPV6, if you can't get another /24.
    – NickW
    Feb 20, 2013 at 10:12
  • I would not use any public addresses for a school intranet or public WLANs. Keep the single network for the servers and possibly multiple NAT gateways.
    – eckes
    May 17, 2018 at 2:33

3 Answers 3

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  1. You can only fit 252 addresses into a /24, one for network .0, one for broadcast .255, and one for a router usually .1 ... the other addresses you can assign.

  2. Whenever you subnet, you lose 3 addresses from that division.

  3. You'd probably be better off using NAT.

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  • Hi, i was thinking to have my Main router as the only one with public address and the rest with private address, is this what u mean by NAT? The main router will be the one connecting to the internet.
    – user2017011
    Feb 20, 2013 at 10:16
  • Yeah, that's what I mean. NAT is a much more expandable solution in your case.
    – NickW
    Feb 20, 2013 at 10:22
  • But how do i implement NAT in my case, considering i have a main router,2 switch,2 accesspoint at lobby, and 1 router, 1 switch , 1 AccessPoint at each floor ( level 2 -6 )
    – user2017011
    Feb 20, 2013 at 10:23
  • If you have a .24, you could assign those addresses to the networking equipment, the routers and possibly the APs, and then have NAT behind them. Switches are usually level 2, meaning they are not concerned with IP addresses directly (in terms of routing). I can give you a bit of advice here, but really, you need to talk to a professional, or possibly take a course in networking.
    – NickW
    Feb 20, 2013 at 10:31
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I guess that the most wanted feature for the network is Internet access, and some hosts will probably need to talk to each other, or you may have some servers in the building, too.

Something you'd probably not want at all is to give each client a public IP. Or at least not without a firewall ;)

From a security point of view, you'd be best off if you had a switch which supports 802.1q VLANs, then you'd assign each host which a single VLAN and NAT them out on the Internet. This way, if one of them gets a Virus or intruder, you won't have all of the others infected as well.

I do understand, however, that this is a bit of an effort, though. As a smaller scale solution, you could at least separate clients and servers using VLANs.

What you will definitely need is a router, hardware routers work fine but are usually very limited.

For ease of use I heavily recommend pfSense. It can do all the NATing you'll need, plus you have good control over who is allowed to talk to whom. All you'll need is a fairly standard PC (we have an old 600MHz P3 and it handles a lot of traffic).

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To add more hosts than 254 you have to go into /23 which has capacity of 510 (1 address 1 broadcast) You can't connect same networks with router, neither with switch cause it will cause conflict. you have to go into /23 that means 255.255.254.0 and your IP's will be 203.218.71.1 - 203.218.72.254

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