# Configuring a switch to bridge two subnets



## reflexx (Jan 19, 2011)

Trying to set up the network at a school. There are two networks in place - network A (10.0.*0*.*) and network B (10.0.*10*.*). Each network will have their own DHCP and file servers.

The _Internet connection feeds into A_. Goal is to be able to configure a switch so that the two networks are essentially kept separate as far as IP addressing goes, but _B can access the Net through A_, and client machines on each network can connect to servers on both networks.

I am experienced with general networking, but haven't addressed this situation before.

Attempt so far is to give the bridging switch (linked to both networks) an address of "B.254" with a mask of 255.255.0.0 and gateway of the network A gateway. Clients on B have the B.254 address as their gateway.

So I'm imagining all traffic on network B will stay within there unless it is for an address on network A or external IP. But I haven't wrapped my mind around how to set things up so the DHCP servers only serve their network.

I'm also having some confusing behaviours when trying to connect to various machines. But that's another point to look at when I've rationalised what's happening.

So, can anyone point me to instructions on how the connection of two subnets is normally done, or does it require a dedicated bridging piece of hardware?

I'll supply model numbers if required, but at this point I can tell you that the switches in use are D-Link, and have the ability to configure VLANs and ACLs if that helps.

r


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## Wand3r3r (Sep 17, 2010)

You can't do what you want to with a switch. You need a router. You can't bridge different ip subnets. You have to route between them. The router also stops dhcp traffic from passing across.


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## reflexx (Jan 19, 2011)

Thanks. It wasn't the answer I was hoping for, but at least it's an easy one to understand :sigh:

So much for the advice I had from a networking expert who suggested it


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## Wand3r3r (Sep 17, 2010)

Sorry to hear that. It can be challenging to get a clear picture of someones network from what they write. Best of luck!


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