Unbound DNS resolution stops working for 192.x subnet

[allenlook]

Normally, everything is working great (25.7.4), but once in a while I'll notice that certain programs on the LAN stop working, and their ability to ping other LAN machines by name is broken (even when that name is their own).  When that occurs, pinging by IP address still works fine, and programs using the Internet still work fine.

Interestingly, on one machine that runs a VPN, I can ping other machines by name but it uses the 10.x subnet through the VPN (which is set to allow LAN traffic) instead of the 192.x subnet that all machines run on normally.

If I restart Unbound DNS then everything gets back to normal.  It had been up and running for 22 days yesterday when I had the problem, and I'd say this happens about once a month-ish.

Should I just automate a process to reboot Unbound DNS every night?

[allenlook]

Happened again yesterday.

Only a restart of Unbound DNS would resolve the issue.

[allenlook]

I added a cron job to restart Unbound DNS every night, and for the past month I've only had one instance where DNS resolution stopped working for LAN addresses. 

Same rate of errors, e.g. once-a-month-ish, but I'd say the past month has been the "quietest" for me in regards to Opnsense issues so far.

[tangofan]

Happened again yesterday.

Only a restart of Unbound DNS would resolve the issue.

Yes  I had the same issue also a few days ago. All the sudden DNS resolution didn't work anymore, but a restart of Unbound within OPNsense got everything back to working again.

Looks like there is some fringe condition that causes Unbound to go into a freeze. I'm wondering how to debug this, when it happens again, so someone can find the root cause of this.

[willj8823]

It may not be related to your issue, but I had a similar Unbound DNS problem (after an OPNsense reboot) with name resolution for internal devices. My issue went away after I started Zenarmor (it was stopped for some reason) and ran a pending Zenarmor update.

As I was sorting through a DHCP issue with my Unifi APs after an OPNsense reboot, I noticed that name resolution was failing for internal devices. I restarted  Unbound and verified that my desktop (dhcp client) had the correct DNS server specified, but I still could not ping any of my internal devices by name. Looking through my Services on the OPNsense Dashboard, I noticed that Zenarmor was not running. I started Zenarmor and ran the pending update. I don't know whether Zenarmor being in a 'not running' state had anything to do with the name resolution failure, but after the Zenarmor update completed, name resolution was working again.

Will