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I'm working by my customer premises and they let me connect my private laptop on a dedicated Wi-Fi for internet access. It's nice for external consultants. The only issue is that we can't connect on a remote server on port 25. I suppose this policy is set up to avoid infected computers sending spam from their network.

As you can have guessed, this is something weird that I can't send mail at all. Fortunately, I've a 3G cell phone that I can connect by Bluetooth on my laptop. So when I want to send an e-mail, I have to disconnect from Wi-Fi, connect my phone, send the e-mail, disconnect phone and reconnect Wi-Fi. Kinda overhead.

My question is: how can I tell Windows 7 to use the Wi-Fi for every out connection, but if it's a connection on port 25, use the cell phone network? With this solution, I could let my phone connected all day without having to switch again and again.

Thanks a lot for your anwwers. Fabian

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up vote 1 down vote accepted

do the below only if you know what you are doing.

  • first open an admin right cmd.exe (i.e. windows key -> "cmd" then right click "cmd" and click "run as administrator")
  • run route print (this should show the interfaces)
  • then run route add dest mask netmask gateway metric metric IF ifcode where dest = destination (the mail server), mask = netmask (in your case is a single IP), gateway is the default gateway of the phone, metric (a small one), and ifcode the interface of your phone.

hope that helps

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Can we add a route only for a specific port and not a destination host? – Fabian Jun 7 '10 at 7:51
@fabianvilers No, the routing table only handles IP addresses. You would need a NAT/firewall which supports routing based on port to do that. I'm afraid I don't know any off the top of my head for Windows. – Darth Android Jun 7 '10 at 8:04
@fabianvilers, i think that is a limitation of window's routing system. @Darth Android is correct. – bubu Jun 7 '10 at 8:54
It's not exactly a limitation - IP routing only deals with IP addresses. Ports (TCP or UDP) are on a higher level. – grawity Jun 7 '10 at 15:40
@grawity, i do agree with you that IP routing only deals with IP addresses, but policy-based routing (as in cisco routers) supports port, of course, so when we are talking about routing capability (in general), i think calling it a limitation is not exactly wrong :) – bubu Jun 7 '10 at 15:56

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