My ISP's DNS servers are sometimes sketchy, so I use 4.2.2.1 and 8.8.8.8 respectively. The Layer 3 DNS server and Google's DNS server.
Sometimes there will be a long delay in resolving, and if I revert to the DNS servers given with DHCP, then everything will be fine for a bit, before I ultimately have to revert back to the 3rd party DNS servers.
Can someone explain this behaviour, or the reasons why this would happen?