Since upgrading the Vigor 2820 in the office to the latest 3.3.4 firmware we have had issues with some Snom VOIP phones registering to our * PBX. The phones showed UDP packet errors, but the packets weren’t making it to the PBX.
Unfortunately we had upgraded * around the same time, so most efforts were focused there rather than on the router. However it appears that 3.3.4 is badly broken for voip, we had issues with Snom and Grandstream devices, a downgrade to 3.3.3 fixes everything!
I can see a few other people have had the same issue since we discovered this, so hopefully one of us will pop into google and save some head scratching 🙂
3.3.3 is still available for download on the draytek site – http://www.draytek.co.uk/support/download/v2820_333_232201_A.zip