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Odd issue with internet access


I did several research and looked everywhere in the firewall, but I was not able to find an answer to my problem. Basically:

- I have an XGS126w with the latest OS

- The setup is fairly simple: 1 LAN on a private /24 subnet --> The Firewall --> Internet connection via the internet provider's gateway

- I set up a MASQ rule and ACL rule for the /24 subnet to access the internet, and but I still have no internet access

- However, as soon as I ping an internet target (like from the firewall (Diagnostics -> Ping -> Ping from my LAN interface), then the internet access starts working from my LAN.

- A few hours later, the LAN->internet access stops working again, and I have to ping an internet target from the firewall diagnostics tools again...

Did anyone see this issue before? I assume something happens when I ping 8.8.8 from the firewall, and I need to configure that thing in the firewall, but I can't figure out why... I'm happy to provide screenshots of my configuration if needed.

Many thanks for your help.


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[edited by: emmosophos at 12:30 AM (GMT -8) on 7 Dec 2023]
Parents Reply
  • Hello there,

    If the issue persists, please open a case with Support and share the Case ID with us.

    I recommend you do a pcap when the issue isn’t happening and one when the issue is happening so support can compare both captures.

    Additionally, do a GUI Packet Capture, showing what firewall rules are hitting the traffic (when it is working) and do the same when the traffic stops working.

    And finally, do a conntrack during both scenarios.

    But it does sound like an issue with ARP, so you might want to check the connection between your Moden and the Sophos Firewall

    That should help support get started with the investigation.


    Emmanuel (EmmoSophos)
    Technical Team Lead, Global Community Support
    Sophos Support VideosProduct Documentation  |  @SophosSupport  | Sign up for SMS Alerts
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