Article:
  VPN on Mac OS X
Subject:   Loss of internet when connected to VPN
Date:   2003-03-12 14:23:42
From:   anonymous2
Having set up VPN to work from Jaguar, much the same as the first part of this article, I find that I loose my internet conection while the VPN is connected.
Digging into the BSD environment I find that it is because it creates a default route via the VPN which overrides the default route to my NAT router.
I cannot find any configuration in either the network or Internet Connect configuration to prevent this.
Is this a known problem.


Alban.

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Showing messages 1 through 4 of 4.

  • Jason Deraleau photo Re: Loss of internet when connected to VPN
    2003-03-12 15:01:52  Jason Deraleau | O'Reilly Author [View]

    Your default gateway is determined by the order of your network interfaces in the Network pane of System Preferences. Whichever interface is at the top of the list will be the default gateway. If that interface isn't availble, the next in the list will be the default gateway, and so forth. What you want to do is be sure that the interface used for your Internet connection is above the one for PPTP.

    To change the order, select "Network Port Configurations" from the Show drop down menu. This will display a screen which allows you to drag and drop your interfaces into the desired order.
    • Re: Loss of internet when connected to VPN
      2003-03-13 11:49:33  anonymous2 [View]

      Thanks for the reply.
      I have checked the order and Built-in Ethernet is above PPTP.
      netstat -r normally gives:
      Destination Gateway Flags Refs Use Netif Expire
      default 192.168.1.1 UGSc 6 4 en0
      127.0.0.1 127.0.0.1 UH 14 3290 lo0
      169.254 link#4 UCS 0 0 en0
      192.168.1 link#4 UCS 1 0 en0
      192.168.1.1 0:20:78:da:e3:e2 UHLW 6 0 en0 868
      192.168.1.50 127.0.0.1 UHS 0 1 lo0

      After connecting the VPN
      Destination Gateway Flags Refs Use Netif Expire
      default 10.1.2.150 UGSc 1 5 ppp0
      10.1.2.150 10.1.2.151 UH 2 0 ppp0
      127.0.0.1 127.0.0.1 UH 13 4107 lo0
      169.254 link#4 UCS 0 0 en0
      192.168.1 link#4 UCS 1 0 en0
      192.168.1.1 0:20:78:da:e3:e2 UHLW 1 0 en0 1092
      192.168.1.50 127.0.0.1 UHS 0 1 lo0
      vpnsvr_address 192.168.1.1 UGHS 1 1 en0

      Note: vpn server address obscured for security
      It appears the VPN ppp0 interface completely replaces the default routing. Reversing the order makes no difference.

      I can set the routes manually each time, but I don't believe this should happen.
      I would expect to get a route to 10.0.0.0/8 via 10.1.2.150 and the default route left alone.
      Note it adds a route via the original default gateway to the address of the VPN server.
      There appears to be no way of setting no default route for the pptp interface.

      Any other ideas,
      Alban
      • Re: Loss of internet when connected to VPN
        2003-11-17 17:40:27  anonymous2 [View]

        I found an automated script for correcting the route here:
        http://www.macosxhints.com/article.php?story=20030313194656474

        works well for me, in panther, after some small mods.

        -millz
      • Jason Deraleau photo Re: Loss of internet when connected to VPN
        2003-03-13 11:53:10  Jason Deraleau | O'Reilly Author [View]

        Hmm. Coincidentally, this hint came through Mac OS X Hints earlier today:

        http://www.macosxhints.com/article.php?story=20030311232930261&mode=print

        It describes how to run pppd to make the VPN connection by hand, allowing you to remove the defaultroute statement. Apparently this is an unforeseen circumstance on Apple's behalf.