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Weird PPPoE behavior

I use a DSL modem which bridges traffic to the Sophos. The Sophos has a PPPoE interface and builds up the connection.

Yesterday I upgraded from a Sophos SG 105 to a 135, since then the PPPoE connections doesn't work anymore. I see many failed tries in the pppoe.log.

The weird thing: when I start using tcpdump on the ethernet interface,  I can see traffic and the pppoe negotiation gets successful. I've noticed this behavior many times.

Any ideas on this?



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  • Hello timreck,

    Thank you for contacting the Sophos Community.

    What are the errors that you are seeing in the pppoe.log?

    Does the modem have any MAC filtering or your ISP might only accept traffic for a specific MAC address? 

    Not sure why a tcpdump would make the connection connect, but if it does, then the PPPOE connection goes down after a while?

    Regards,


     
    Emmanuel (EmmoSophos)
    Technical Team Lead, Global Community Support
    Sophos Support VideosProduct Documentation  |  @SophosSupport  | Sign up for SMS Alerts
    If a post solves your question use the 'Verify Answer' link.
  • Hi emmosophos,

    the output of the pppoe log:

    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: No response to 10 echo-requests
    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: Serial link appears to be disconnected.
    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: Connect time 4.1 minutes.
    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: Sent 910817 bytes, received 67335642 bytes.
    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: Script /etc/ppp/ip-down started (pid 17944)
    2020:06:16-21:30:18 atlantis pppd-pppoe[16814]: sent [LCP TermReq id=0x2 "Peer not responding"]
    2020:06:16-21:30:19 atlantis pppd-pppoe[16814]: Script /etc/ppp/ip-down finished (pid 17944), status = 0x0
    2020:06:16-21:30:21 atlantis pppd-pppoe[16814]: sent [LCP TermReq id=0x3 "Peer not responding"]
    2020:06:16-21:30:24 atlantis pppd-pppoe[16814]: Connection terminated.
    2020:06:16-21:30:24 atlantis pppd-pppoe[16814]: Modem hangup
    2020:06:16-21:30:24 atlantis pppd-pppoe[16814]: Exit.

    My modem has no MAC filtering, I can even see the right Sophos' MAC in its ARP Table.
    And as the mac of my modem didn't changed, I sure my ISP is not blocking any traffic because of some mac change.

  • OK, some progress: the problem seems to be fixed when I set the WAN interface into promiscuous mode... 
     
     
     
  • Hello Timreck,

    Thank you for the update on what solved the issue.

    Regards,


     
    Emmanuel (EmmoSophos)
    Technical Team Lead, Global Community Support
    Sophos Support VideosProduct Documentation  |  @SophosSupport  | Sign up for SMS Alerts
    If a post solves your question use the 'Verify Answer' link.