Q. I've configured Routing and Remote Access to connect two subnets, but clients can't communicate to servers via the router. What's wrong?

John Savill

April 30, 2009

2 Min Read
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A. First, make sure you have your Routing and Remote Access server configured correctly. Remember:

  • Make sure you've enabled the router function for LAN. Navigate to Routing and Remote Access manager, then Server properties and in the General tab make sure Router is checked.

  • Make sure IP routing is enabled. Navigate to Routing and Remote Access manager, then Server properties, and in the IP tab make sure Enable IP routing is checked.

  • No NICs should have a default gateway defined. You should, however, define a static route on the NIC that connects to another default gateway if you have one on your network. The static routes settings, shown here, are located in Routing and Remote Access manager under Server, then IP Routing, then Static Routes, then destination, subnet. Enter the gateway address and select the adapter.

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You might be using Routing and Remote Access to connect two subnets when it isn't the default gateway for clients on both sides of the router, such as if you have a branch office that accesses the main location via a Routing and Remote Access server. In this case, Routing and Remote Access is the default gateway for the branch computers. The computers in the main location, however, have a different gateway to the Internet. The computers in the main location have no way of knowing how to get traffic back to the machines in the branch. To resolve this, you need to add a static route on the computers in the main location so they know how to get to the branch subnet. For example, use the command

C:>route add MASK METRIC 1 IF 13OK!

In this example, I'm telling the client that to get to the network, I must send the traffic to address on interface 13 (Interfaces are listed at the start of a ROUTE PRINT execution). Adding this route resolves many problems where you have this combination of subnets being connected without common gateways that are configured to share routing information. The results of this command are illustrated here.

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An alternative would be to update the gateway of the clients to know how to route the traffic to the remote subnet. Updating the gateway would be a better solution for large numbers of clients.

Related Reading:

Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.

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