The main issue with the Unlimted Horizon service on the Draytek 2820 Router is UDP fragmentation this can cause issues with DNS resiliency. The following solutions are recommended:

  1. 1. Download the latest firmware from Draytek which should contain a patch to solve the problem with UDP fragmentation
  2. 2. Specify the DNS servers in the Draytek LAN Config to a 3rd party DNS server such as Google (8.8.8.8)