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Advice needed on subnetting


I'm working for a small company where i want to create some subnets, 1 subnet for the servers, 1 for main office and 2 subnets for other offices

This is what i had in mind: = server subnet (10 servers) = main office (30 workplaces) = other office (10 workplaces) = other office (10 workplaces)

Now is the question what subnetmask i need to use... most simple should be but i'm affraid i will get bad performance because broadcasts and so.

Please advice, i'm a beginner in subnetting.

4 Solutions

with the given networks and the subnetmask it will be a "flat" network, meaning just switches no routers. If that is what you intend, is O.K. Otherwise you need a router with 4 interfaces, where each interface has one ip address in one of the networks. Then you will use as a network mask for each of the 4 networks.

If you are worried about broadcasts in a "flat" network, you can just forget it in a setup with just that few computers you mentioned. However, if you plan to grow, you should consider to use a router now, as this gives you more flexibility, although it's more effort to set up.

You can use a pc with linx as router or buy a cheap router from cisco, 3com, HP, linksys, netgear, etc. It just depends on your preference and the budget.


kukno is on the right track, but needs just a bit more clarification.  An IP subnet is defined by is subnet mask.  What you are proposing is not  subnets, but 1 subnet with IP ranges defined for specific uses.  Which is a common practice.  

Now, you mentioned "offices".  Are these offices at the same physical location as the main office, or at different physical locations?  If they are at different physical locations, then you will need a unique IP subnet for each office.  You will also need a way to connect the offices.  With the number of computers you have quoted, the least expensive would be to get each office an Internet connection and setup VPN's between them.  If you plan to have your users be able to VPN in from their home, then you should also change what IP subnet addresses you are using.  What I would suggest is: mask   Main office mask   Remote office #1 mask   Remote office #2

Then within each range reserve address for specific uses, such as:

   .1-.10    Network devices
   .11-.20  Printers
   .21-.50  Servers
   .51-.99  Future Use
   .100-.200 workstations
   .200-.254 Future Use

There is no mask that precisely covers the range you specified...

The subnet mask will give you through on one network though.

Still, if you want to be ready for it to actually grow to 1022 devices, you should go with a router and keep the networks separate as kukno and giltjr are counseling.

Before you get 500 devices on it you'll be seeing a LOT of broadcast traffic on a /22 network.
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juriangAuthor Commented:
Ok, first off all thanks for the answers!!

The other 2 offices are indeed remote offices so the plan is to use routers and setup a VPN.

question: is it correct that i have to configure the routing table on each router and add all ip ranges?

i'm new to this so if i forgot to mention some information just let me know.

You are correct about the routing tables.  In each office's router you need to route statmentes to get to the other offices subnets.
juriangAuthor Commented:
Thanks, i'm going to try it.
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