Does this sound like a bug to you – DHCP issue

I have been working with sonicwall for close to 15 years, I have never seen this issue before.

We implemented a new firewall at a site and the DHCP was set to 5 minutes mainly to give us a window to make a change to the DHCP, if needed, w/o requiring us to wait 24 hrs for the changes to kick in. We also do this when we have to change DNS servers and/or other DHCP parameters and the existing lease is set to 3 days, for example, we will change it to something much lower than 3 days so we can make the change, client devices get the new settings and then we change it back to 3 days.

This has worked very well over the years up until recently (this year). This site was set to 5 min DHCP and we forgot to change it to the default of 1 day or 3 days, we typically match the previous firewall that was in place.

No issues that we noticed right away, but a few days later some users complained that they would randomly see pages drop connection/not load/lag/etc. It wasn't every user and it was never the same site. After a few days of troubleshooting, we didn't think to check the DHCP lease time settings because we thought we put it back to the standard setting, but we figured this would be a good time to put it back to the normal setting of 1 day and the issue went away.

Also, I want to confirm, here, that it was not dropping every 5 minutes when the DHCP lease was set to renew and, as already stated, it wasn't the same user.

Sonicwall lets you set the DHCP renew time under 5 minutes, if that were a known issue then I don't think sonicwall would allow the value of 5 minutes.

Previous years, we've had it set to 5 minutes and left if that way for weeks (for other reasons that aren't needed for this post) and never experienced any issues. Once we finished, we changed it back to the regular time, during that period there were no disconnect issues.

Does this sound like a DHCP bug or were we just extremely unlucky? The firewalls have all been updated since this incident occurred, I'm not sure which firmware we were running, but it was fairly recent. Firewall was NSA 3800 with HA setup. Yes, we did rule out the HA, also had dual WANs, we ran the HA setup with a single WAN to make sure the firewall wasn't failing over or experiencing a routing issue with the primary WAN. We changed the WAN ordering, but we also disabled the WAN interface just to confirm it wasn't WAN related.

The issue has not re-appeared and the last change made was changing from 5 min DHCP lease to 1 day DHCP lease.