Sophos Firewall v20 -- DHCP IPv4 Lease Table is empty

Hi Alan,

Thank you for reaching out to Sophos Community.

This might be a possibility of a known issue - NC-126965. We request you to reach out to Sophos Support to log a case so that this can be further checked.

Also, kindly see a similar post as a reference 

•  Dhcp ip release and web page hang issue 

After rebooting my Sophos Switch, it's IP address now shows up in the DHCP lease table.

After setting my Windows machine to use dynamic IP assignment, it's IP address now shows up in the lease table.

After rebooting my Sophos Switch, it's IP address now shows up in the DHCP lease table.

After setting my Windows machine to use dynamic IP assignment, it's IP address now shows up in the lease table.

Hi Alan,

Thank you for the update and for sharing the information.

If the issue re-occurs, I would recommend creating a case so that this would be further checked for the root cause.

Hello Alan,

Thank you for sharing an update. Few more insight might help to understand problem in a better way.

SFOS does not support DHCP leases persistence across reboot. If you have given a lease for 1week (for example) to any client (windows or Sophos switch), client will not renew it until half-time is passed - in this case 3.5days.

With this behavioral background, if you have upgraded SFOS to v20 and looking at DHCPv4 lease table, you won't see it immediately as we are not persisting it and client won't renew it until its lease is about to expire. And when you would have rebooted Sophos Switch or windows machine, it might have come to confirm/renew its lease and that's how DHCPv4 leases could have been seen in the UI.

You can confirm this behavior by rebooting the SFOS again (whenever you can take a downtime). If behavior is similar to what I have mentioned than it's expected behavior and not specific to v20.

Hope this helps.