DHCP DNS servers still get routes even if allow override is unchecked
If you have hardcoded DNS servers and uncheck "Allow DNS server list to be overridden by DHCP/PPP on WAN", DNS servers assigned by the DHCP server on a WAN are still given routes even if they are not added as system DNS servers.
Easy to reproduce by adding some DNS servers, unchecking the option, and then watching the routing table. The DNS server(s) assigned by the DHCP WAN show up in the routing table with a MAC (not an IP) as the gateway.
Ticket #1408. Do not add static routes for automatically learned dns servers from dhcp if Allow override is not selected.
#2 Updated by Jim Pingle about 8 years ago
Seems like a pretty bad bug if you checked the option to ignore the DNS servers and yet they get static routes. I'd prefer to see a fix in 2.0, I don't think anyone would expect or have been relying on this misbehavior.
The problem I had with it is that I wanted to route 188.8.131.52 over my DSL, and had set the GUI to do just that. However, my Cable provider started handing out 184.108.40.206 as a DNS server over DHCP, so dhclient added a route to 220.127.116.11 over Cable, even though the GUI was set to route that over DSL. This led to an inconsistency in the GUI such that I chose to do two specific things (route this IP one way, and disallow override) neither of which really happened as expected.
I worked around it by flipping the WANs I had assigned for each of those servers, but if my cable provider starts handing out 18.104.22.168 as a DNS server too then I'll be stuck again and have to pick another DNS server, since dhclient isn't honoring the "do not override" setting.