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Internet vs LAN2LAN VPN DNS issues for IMAP connection.

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  • Internet vs LAN2LAN VPN DNS issues for IMAP connection.


    We have a member of staff who works from a remote location. If she connects to the Internet and fires up Thunderbird, she can access her work email via IMAP without a problem. The IMAP connection uses our public IP address for the IMAP and SMTP server addresses and our gateway router uses port forwarding to forward IMAP/SMTP traffic to the email server. That works fine.

    However, she also has access to a LAN2LAN VPN connection. When using this she fires up Thunderbird and nothing happens - from her description it seems that the IMAP traffic is simply not reaching the mail server. Note that when connected via the LAN2LAN VPN she can access the Internet without any problems. I don't have any further info at present.

    The LAN2LAN is configured so that she connects to a Draytek router hosting a wireless network at the remote office. The wireless network is on a completely different subnet to the rest of the office (this is used so that her usage is separated from the rest of the office - politics!). Traffic from the wireless network is routed to a WAN connection (which is the remote office's network) which is the start of the LAN2LAN VPN - the WAN connection specifies the remote office gateway for outgoing traffic. The LAN2LAN VPN terminates at a Draytek router at our office inside our network.

    When connected via the LAN2LAN VPN should the IMAP traffic be delivered to our network, then leave via our gateway and then return to our network (i.e. go out and come back in again) so that our router can then process the incoming IMAP and SMTP traffic? But, isn't this traffic routing happening already when she browses the Internet?


    Can anyone shed some light on what is happening here, please? I'm sure I'm missing something really basic.
    A recent poll suggests that 6 out of 7 dwarfs are not happy

  • #2
    I would hazard a guess that the VPN tunnel is set to send all internet traffic via the VPN.

    What is LAN2LAN? Is it a piece of software?


    • #3
      LAN2LAN VPN = A VPN connection that links two separate LAN's together so that you can access both networks.

      The Draytek is configured so that all traffic is routed from the wireless network to the LAN2LAN VPN. Sorry, I had a hell of a job setting this up so am probably not describing it very well. All the gory details are here.
      A recent poll suggests that 6 out of 7 dwarfs are not happy