Strange issue with a 2820 router.

We have it connected to a BE line with MPoA/1483 Bridged IP LLC setup. Running latest 3.3.5.1_232201 firmware.

The line is at times heavyly used in a hospitality environment.

The router appears to stop routing all DNS traffic, we have checked and all ICMP, TDP/ UDP passes but DNS stops working.

We need to reboot to bring it back to life.

Odviously this isn't good.

Mark Simcock

I get this also on a 2820 with Zen.

Various firmware from 3.3.1 upwards - although the newer the software, the more frequent the failures.

It does seem to be related to higher usage as it will go two or three days during the week but may need several reboots over the weekend, when usage is much higher.

Just stops passing DNS traffic altogether.

Check whether you've got the UDP flood defense enabled on the Firewall - DoS Defense page? If there's enough DNS requests, that could get triggered and cause exactly what you're seeing.

Many thanks for this.

I disabled the UDP Flood Defence on our router and it has been stable for a couple of weeks now (previously it would only last a couple of days).

Seems to be a little faster as well, but that may just be subjective.