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Thread: VPN related question

  1. #1
    Join Date
    Jul 2011
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    10

    VPN related question

    I have configured the pptp server on ubuntu 12.04 and these are the logs that I got when I connect to it through vpn client (win xp).
    Dec 6 19:35:00 ubuntu pppd[1145]: Using interface ppp0
    Dec 6 19:35:00 ubuntu pppd[1145]: Connect: ppp0 <--> /dev/pts/0
    Dec 6 19:35:00 ubuntu pptpd[1144]: GRE: Bad checksum from pppd.
    Dec 6 19:35:02 ubuntu pptpd[1144]: CTRL: Ignored a SET LINK INFO packet with real ACCMs!
    Dec 6 19:35:02 ubuntu pppd[1145]: peer from calling number 10.10.10.254 authorized
    Dec 6 19:35:02 ubuntu pppd[1145]: MPPE 128-bit stateless compression enabled
    Dec 6 19:35:02 ubuntu kernel: [ 98.375862] PPP MPPE Compression module registered
    Dec 6 19:35:05 ubuntu pppd[1145]: found interface eth1 for proxy arp
    Dec 6 19:35:05 ubuntu pppd[1145]: local IP address 172.16.10.1
    Dec 6 19:35:05 ubuntu pppd[1145]: remote IP address 172.16.10.234

    I want to ask that it is succesfull connection or not?
    I have doubt on two things?can somebody explain it.
    1)GRE: Bad checksum from pppd.
    2)CTRL: Ignored a SET LINK INFO packet with real ACCMs!
    thanks

  2. #2
    Join Date
    Nov 2008
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    Metro Boston
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    9,041
    Distro
    Kubuntu 14.04 Trusty Tahr

    Re: VPN related question

    Can you ping the remote's IP address, 172.16.10.234? If so, you are connected; if not, well....

    If there is a firewall running on the remote, it needs to allow GRE traffic. I think you have to add an iptables rule to allow the GRE protocol. Do a little google searching for "gre iptables".
    If you ask for help, please have the courtesy to check for responses and thank the people who helped you.

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  3. #3
    Join Date
    Jul 2011
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    10

    Re: VPN related question

    Quote Originally Posted by SeijiSensei View Post
    Can you ping the remote's IP address, 172.16.10.234? If so, you are connected; if not, well....

    If there is a firewall running on the remote, it needs to allow GRE traffic. I think you have to add an iptables rule to allow the GRE protocol. Do a little google searching for "gre iptables".
    SeijiSensei thanks,

    I disabled the firewall and also allow the gre traffic from my edge firewall (which is mikrotik), but still it is giving me the gre bad checksum error.

    yes i can ping to my default gateway, in this case 172.16.10.1

  4. #4
    Join Date
    Nov 2008
    Location
    Metro Boston
    Beans
    9,041
    Distro
    Kubuntu 14.04 Trusty Tahr

    Re: VPN related question

    I'm afraid I cannot help much more. It's been years since I ran a server that supported PPTPD. Nowadays I use OpenVPN tunnels which are orders of magnitude more secure than PPTP.

    If you enter the error text into Google you'll see other discussions. Searching for "GRE: Bad checksum from pppd" brings up a number of entries. That's always my first step in diagnosing problems.

    The fact that you can ping the remote means the tunnel is working, regardless of the reported errors.
    Last edited by SeijiSensei; December 6th, 2012 at 06:49 PM.
    If you ask for help, please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

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