Weird DNS issues on some of the switch

[youzhi]

After all the switches are boot up after the power failure in the server. I notice that my stack switches some of the member switch got this alert message indicate DNS is misconfigure. Solution i force reboot the switch having this issues by unplug the power cable and plug back. After the switch is being force reboot, the issues does not happen anymore.

Does any one know the root cause of this?

[jdsilva]

The 'Bad DNS' error condition is a result of the device not being able to resolve DNS queries properly using the configured settings (DHCP or static). 

Sometimes this error comes up after a very brief period where DNS resolution was an issue, but has since cleared. You can easily confirm by going to the 'Tools' tab on the device status page and use the ping utility to ping something by name. If it works then your alert is probably just stale. 

Often this error will clear on its own after some period of time. 

[Nash]

If you can resolve names correctly from the device and the error lingers for an hour or so, I wouldn't worry too much. I've had it take 90 minutes before. Same with bad gateway.

Like, device passed traffic fine! I could talk to it on the dashboard. It was cool. The error just didn't wanna clear.

[youzhi]

Nope it cause my network down, my whole infra LAN & wireless cannot access to internet. until i reboot the switches having the dns misconfigure issues, then able to solve the issues.

[SoCalRacer]

Do you have the DNS info captured from after power outage and after fixed reboot? Both from MX and switch. I have a feeling something is changing DNS wise after that reboot.

[SoCalRacer]

My guess is that the switch boots faster than the server which I am assuming is the DNS server, when the switch boots it can't reach the server. After the next reboot it can since the server is probably fully booted.

You probably should have some UPS on the server and switch to help with this if you don't already.

[Lsims]

I am having the same issue.  College campus, each building is basically a network.  I am only seeing the issue on stacked switches and the issue only shows up on the switches in the stack that don't have the uplink.  For instance, I have 4 switches in a stack, switch 1 has the fiber uplink and 2, 3 and 4 are using switch 1's uplink.  2, 3, and 4 have a DNS Misconfig error and won't forward packets.  Switch 1 isn't reporting the error.  Having this issue across 8 buildings/networks.  At my science center, I have 46 switches but only two stacks, a stack of 2 switches and a stack of 6 switches.  Switch 1 in each stack has the uplink and is fine but the others are error'd out.  Also, the other 38 switches have no errors, every switch in the building goes back to a Cisco 9500.

Did you find a solution to your issue? 

[NFL0NR]

any resolution?  We seem to be having a similar issue with a meraki stack and a Cisco 9300 as the uplink.  

Top switch is a Meraki Core switch.. during it and every other switches "down time" we had it going to a Catalyst 9300.  the Stacked switches were saying DNS misconfiguration.