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A few questions regarding VPN's.

  1. When I ping a remote host (google.com) by IP address, are the packets sent through the local gateway or the remote gateway? Where are these packets routed by default and is this a configurable setting?

  2. Does my VPN tunnel need to be on a different subnet than my local network? And...

  3. How are DNS queries resolved? Once again I wonder where these queries are forwarded to when there are two networks present.

Thank you for your expertise and knowledge on the matter.

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Yes, the setting is configurable. In Windows, the default setting is to route all traffic over the VPN, but you can uncheck a box in the advanced TCP/IP settings for the VPN connection to disable that feature:

  1. right-click on your VPN connection and click Properties
  2. click the Networking tab and double-click on "Internet Protocol Version X (TCP/IPvX)"
  3. click Advanced...
  4. check or uncheck the checkbox for "Use default gateway on remote network"

    advanced TCP/IP Settings dialog in Windows 7

  5. Click OK on all dialogs to save the settings.

(Note that you'll want to repeat steps 2-4 for both IPv6 and IPv4. All ISPs currently use IPv4, but many have started transitioning to IPv6 and already support it.)

Unchecked: VPN will only be used for traffic to/from the remote network, and all other traffic (including Internet traffic) will be routed through your local network.

Checked (default): VPN will be usd to route all traffic outside of your LAN.

share|improve this answer
    
I see. So it would make sense to put my local network in a separate subnet? – Scandalist Oct 5 '12 at 20:18
    
That depends. This is near the limit of my experience, but I think if the VPN link is a permanent bridge between the two networks, then it may be okay to have them share the same subnet--assuming you can guarantee there won't be any hostname or IP address collisions. But I suspect since you're setting up the VPN connection on your computer rather than on a router, you aren't trying to bridge the networks and thus should assign two different, non-overlapping subnets. – rob Oct 5 '12 at 20:29

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