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Challenge of connecting 2 subnet

By abubin ·
I have an existing LAN running at C class subnet with 2 win2k server. Both running with active directory and DNS. There is one linux firewall connected to internet which is serving internet services to this network.

I have now setup another network running on another ADSL router. This is basically a wireless router with 4 LAN port. It's main usage is to serve people with wireless connection.

My main question is how do I make it possible for those with wireless to connect to the main domain? What additional hardware do I need?

I thought of 2 methods but both have some limitation. Please share any idea you may have.

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by rawright In reply to Challenge of connecting 2 ...

While there isn't enough info here to make a definitive answer, the process is fairly straightforward. I just did something similar two weeks ago at work. First off, the new LAN should use the same IP subnet as the existing LAN for simplicity's sake. If that's not possible, you'll need a router between LANs to make the connection. You can do this statically, or configure whatever device is handing out addresses to use a block of addresses within the existing subnet. If the Win2K LAN is using DHCP to assign addresses, you'll want to reserve this block to prevent it from being dynamically assigned to other hosts. The wireless routers I've seen handle address assignments for their wireless clients - you may have to change that, as two DHCP servers can't exist on the same subnet. With such a small network I'd start out with static addressing for all hosts, then experiment with changing them to dynamic assignment after all the basics work.

Connecting one of the wireless router LAN ports to the hub on the existing LAN will require a cable between them, and you may need to configure the wireless box to forward packets across that interface.

When I connected two networks together I ran into a problem that I should have expected, but overlooked. Whoever set these systems up cleverly named the server in each group SERVER. The moment I connected them, everything failed - panic time. Each host name must be unique before you make the connection, and changing names can be tedious. If any devices or services are accessed using UNC names instead of addresses, you'll have to reconfigure them after the change; in my case that meant a lot of time in the Registry of the the servers manually changing addresses. Hopefully you won't run into that.

If you want to give the new network hosts access to the Internet via your Linux firewall/router, set the default gateway addresses of the new hosts to the local (LAN-side) address of the Linux box.

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by abubin In reply to

This is one of the solution i have thought of. A few problem arises from this. The new wireless LAN is using a different internet connection. This will create problem to put the DNS entry for the wireless LAN. If I put it to my existing LAN's DNS, I would be relying on old LAN for DNS resolution. I would like to keep the internet access on both LAN to be as independant as possible.

So using a bridge would a better method but would complicate things a lot. So far my first choice is connecting the new wireless LAN to the linux server (add another NIC) and using that linux as a bridge between the new and old LAN. But I am not very sure if I would encounter any problem with this method.

Thanks for the reply.

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by shawn In reply to Challenge of connecting 2 ...

Not sure if this could work, but let's give it a shot....

For the clients that connect to the wireless router, assign them a different default gateway address than those on your wired LAN. For example:

The clients on your wired LAN should be using your Linux firewall IP as the default gateway address. This means that wired clients will route traffic destined for outside of your network (ie. anything Interent related) through your Linux box. Wireless clients shoudl have a different IP assigned for their default gateway - the IP of the router connected to the second (not sure if you have 2 ADSL lines, but I'll assume it)ADSL router. Any traffic that is destined for the Internet from your wireless clients will then be sent to this 2nd ADSL connection.

To make the 2 LANs (wired and wireless) talk to one another (to get access to servers and printers and the like), you just need to make sure each LAN is using the same IP subnet. It can get tricky if you're using DHCP, but this should work.

Hope this helps.

Cheers,
Shawn

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by abubin In reply to

yes already did what you said in assigning each client with their respective gateway.

And I know I need to do what you stated in connecting both LAN which have same subnet. One is 192.168.10.x and 192.168.11.x. I do know I need to bridge both of this subnet but how? I can't just connect a wire between both LAN's router. It doesn't work that way.

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