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Thread: Routers and VPN mangle my connections

  1. #1
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    Routers and VPN mangle my connections

    Hi... total network newbie here... but, I work from home and need to VPN into my new company (from CA to FL).

    I can connect fine using VPN, but then occasionally (like 5 times a day) the connection gets mangled. It does not drop though. If I check the VPN connection, it says it's up. Network connections (I'm on Windows) says the connection (wired) is fine. But, no internet access, no internal web site access, no email.

    As soon as I disconnect the VPN, all the internet access (and email naturally) comes back. I can then reconnect VPN and get to the internal sites. Until the next time this happens, of course.

    This is also true if the laptop is using wireless, although then the network connection does show disabled, but enable does not work, until the VPN is disconnected.

    I have two broadband connections at home, and this happens on both. The old one is ATT DSL with a Linksys router and I don't recall the modem brand. The new one is Comcast Cable with a Belkin (N1 Vision) router and a Motorola modem.

    The DSL is 802.11g, the Cable is 802.11n.

    I know the router is part of the problem because if I bypass it, and go directly into the modem, the problem does not occur.

    Does anyone have any insight into the cause? Is it some router configuration issue? I have poked around on the Belkin but nothing seems to stand out. Other posts here have talked about PPTP passthrough, but I saw nothing except Belkin believes PPTP is used in Europe.

    One last item. In my old job, my old laptop could VPN in on the DSL and stay there for days and days with no problems. Since the new laptop cannot, it seems like it has to be something with the laptop or the new job's VPN server, but I cannot convince IT of that yet.

    BTW, old laptop Dell, new laptop Lenovo. Just in case that matters.

    Oh, one last thing. I am using the Windows VPN client. We tried installing and using a Cisco VPN client. Interestingly, that caused the connection to mangle immediately! Every time.

    Any help greatly appreciated. Thanks for reading this far - I just wanted to give as complete a picture as I could.

    thanks,
    dc

  2. #2
    Moderator YeOldeStonecat's Avatar
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    The DSL setup, what make/model modem is in front of the Linksys router? Most DSL ISPs now are shipping combo modem/routers..which already do NAT. If you add your own router behind that, you end up with a double NAT setup. VPN traffic does not get along well with NAT. If you use your own router, the ISP supplied combo modem/router should be reconfigured to run in bridged mode, so it's not doing any NAT..basically an old style dumb modem. Have your router do the PPPoE and obtain the public IP.

    Cable..that's no problem there, the Motorola modems are usually just pure modems.

    With many of the Linksys routers, when you poke around the web admin interface, there is a section where you put a check in the box for allowing VPN traffic to pass through. I haven't seen one of those Belkin N1 routers in a while, so I can't remember if they have that setting or not. This setting here basically tells the router to allow VPN traffic to pass through the router unmolested by NAT.

    Also try ensuring the routers are running the latest firmware.
    And you can try fiddling with the MTU on the routers....they're probably set to "Auto"...you can try manually setting them..for the DSL put it at 1492, for the cable set it to 1500.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  3. #3
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    Thanks for the reply! The DSL modem is something called SpeedStream. Both it and the Linksys router are way old.... must be closing in on ... well, well past 5 years. Maybe 7. Maybe more. I don't think there is any problem with it because I ran VPN successfully for days at a time, literally, in my old job using a different laptop.

    But I really need the solution for the cable since that is now my means of connecting to work.

    I did check and the Belkin router's firmware is up-to-date. I have trolled through the interface for the Belkin and have not yet found anything for the VPN passthrough. That would be too simple! I also can find nothing about setting the MTU. I'll try googling those things and see what I can find out.

    New England shoreline... how much snow to shovel?

    thanks!
    dc

  4. #4
    Moderator YeOldeStonecat's Avatar
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    I'll try to take a look at the Belkins user manual over the weekend...see if I can find those settings in there somewhere.

    Southeast CT didn't get much snow...4...maybe 6 inches...hard to tell what fell, it started turning to web snow falling and melting as it accumulated. Wasn't really bad....one of the more "overhyped" snowfalls in recent times though.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  5. #5
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    Thanks.... just an FYI, I found this on a review at Amazon. Not sure what it all means...

    "Doesn't seem to do transparent ipsec tunneling over UDP either with Cisco Windows Vista Client or Cisco WinXP client. Switching back to a Linksys router, I get a VPN connection no sweat. Belkin tech support says I have to create a virtual server with an open port to match my work VPN server (IT says no go - it's security violation to reveal the ports they use). Belkin says opening the ports will create some security risk so I should close them whenever I'm not using VPN - what a drag compared to transparent VPN connections with my old Linksys router. A Google search shows that other people complain about VPN problems with Belkin routers. "

    Just don't want you to waste your time on a Sisyphean task. Of course, Belkin TS could have been clueless.

    I am in CA and, poor me, am just grateful to have seen the sun the last couple days....

    Thanks again,
    dc

  6. #6
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    Did you ever find a solution for this? I have a similar problem.

    My setup is Comcast cable modem/Belkin N1 router. I have my desktop and work laptop wired to the router. I connect to work with Cisco VPN client. Everything runs smoothly until someone else in the house accesses the wireless network. Sometimes the connection disconnects, but mostly it just slows down to where I can't do anything. Outlook gives a message that it cannot retrieve data. I can also make the problem happen by turning on my portable wireless Sirius unit. So the problem is definitely caused when wireless devices are enabled. I thought I'd pass this on in case this could be related to your problem also.

    I haven't figured out what to do just yet. I don't see any VPN settings in the router configuration. I'm going to keep on looking for a solution and will pass on if I find it. Any suggestions would be greatly appreciated

  7. #7
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    My problem was actually the Belkin N1 router. It does not support VPN pass through. I ended up getting the Cisco WRT610N router and that worked fine.

    Meanwhile I have a perfectly fine Belkin N1 that I have no use for.... :-(

    cheers,
    dc

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