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Connecting 4 networks

Hi Experts

I've got four networks (which I will refer to them as sub networks) each one of them has a number of computers that varies form 4 to 12

the computers in each sub network are connected to each other by a hub/switch

What I want is to connect these hubs to make a big network so the sub networks can share files and internet connection

I also want to have the ability to disconnect any sub network from the main network so it can function by itself

Someone said to me that I should use a router or a computer with multi NICs as a router to achive this goal

I would like to know the best way to connect the four sub networks to each other and a tutroial here or a url explaining how I should set this up because I'm a beginner in network
1 Solution
First I wouldn't use hubs, I'd use switches.  And do you have a domain in place where you can setup trusts and put the pcs on the same IP scheme.

Here is a reference for step-by-step instructions on setting up a domain and sub domains

Recommend using a router for simplicity.  If you are well versed in network OSes (such as Linux or Windows server) you could also use a single PC with muliple NICs.  
One big router would be preferrable, but there are several possibilities:

1) Single router with multiple interfaces:

                /    |    \
         LAN2  LAN3  LAN4

2) Multiple "broadband" routers:


3) Some routers (i.e. Cisco) support secondary IPs so that you could technically use a dual-ethernet router for all four networks:

I haven't tried this with FOUR networks, but it should work:

Ok, this is FOR SHARING INTERNET ONLY.  If you need to share files between networks, I would advise you to pick up what is called a "layer 3 switch" for your core switch to route between networks.

So, you get 5 broadband routers like this one:http://www.linksys.com/products/product.asp?grid=34&scid=29&prid=561 .  BBR1-4 would have their WAN port connected to a LAN port at the head end router.  The head end router would need static route statements back to the four networks.  The pseudotext (get it? ;) ) for this would be something like:  destination LAN 1 next hop WAN port of BBR1.  

So, if BBR1 WAN port has a static IP in the range of <.100 (I would do something really easy like making LAN1 .10, LAN2 .20 and so on) then the static route would be something like this: (this is saying for network 192,168.2.0 with a mask of then send it to the next hop of

As a matter of fact, turn of DHCP on the head end router.  Leave it on for the other four routers.

If you need some more help, post here.  Also check out http://www.practicallynetworked.com.
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iHadiAuthor Commented:
Thanks all for your replies and I'll apreciate any more replies,sollutions and tutorials

ruddg ,
I preffer the first possiblity because its easier as I think. Can you recomend a good router with secure firewall that could match up for connecting 4 networks or more. I'd prefer an easy to conifgure one. And I'd prefer it with a builtin firewall

I do not know what options may exist in the lower strata of routers, but I would be looking at a Cisco 2821 for a business-class solution:


Depending on your current Internet access technology, you can outfit this with a T1, ISDN or ADSL WIC for connectivity and add a couple ethernet ports to dedicate one interface per subnet.

Important note: if any of your four subnets currently share the same IP space, you will need to renumber or integrate them.
iHadiAuthor Commented:
I think we are using dynamic IPs so is it ok

What do you mean by adding ethernet ports
The 2821 comes with 2 fastethernet ports built in.  You would need to add 2 more ethernet interfaces for the additional subnets.  I am talking about the IPs used on your internal networks -- if they are using the same subnets (i.e. then you will either need to integrate the subnets or renumber one or the other of them.
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