sudden loss of dns

[macsolutions]

I've got one device on my network that randomly, and suddenly, loses its connection to the internet. Full stack Meraki; wired and wireless interfaces are affected.

The short term fix is to change the DNS from the Meraki DHCP assigned address to something else.

Device is an iMac 24" M1, running 12.3, but the problem has been around since release of the iMac when it was running previous OSes.

When it fails, WiFi only devices, such as an iPad, continue to work.

This means it only affects the one wired device on the network - the other wireless users either never notice it or never complain - and that includes just one portable device and a few TV's. And the TV's are ALWAYS on, so it seems to be just affecting the iMac.

It is completely random - there is no way to do a packet capture when it happens - but it happens 1-3 times per month.

Any ideas on tracking this down?

[Brash]

When the issue occurs, how long does it take before it resolves itself?

If there's time available, you can capture on the Mac and on the Meraki side to pinpoint whether DNS requests aren't being sent or aren't being replied to.

It would also be interesting to see if the issue happens on the Mac when cabled and having the wifi disabled (or vice versa)

[macsolutions]

I've never waited that long. When it stops working, I start looking for answers. The first few times by rebooting, then digging deeper, only to discover that changing the DNS fixes it (after I realized pinging the IP address worked, but the name did not.

I will try to capture packets on the machine next time it happens.

[BrandonS]

This issue feels vaguely familiar to me from my own Mac experience.  I can't recall the resolution, but I think it had to do with another application breaking something with DNS. Maybe a VPN client?  Or maybe VMWare or Parallels? I used to use a lot of different VPN clients on my machine to support various clients.  Sorry I can't remember details, but maybe that helps a bit to consider some apps that might be capable of breaking DNS..  Maybe a clean install with minimal applications installed for a while to prove the point if feasible?

[BlakeRichardson]

Brandon had some really good suggestions, when the fault occurs can you ping 8.8.8.8 from the affected machine to confirm that its just DNS and not full network access?