I am running RUTX_R_00.07.02.7 and having some issues with DNS resolution. The symptoms to start with were that the router couldn't connect to RMS or check for software updates, and trying to ping a destination showed every address resolving to 198.18.1.1. Using the CLI and specifying the Google DNS servers in a lookup resolved without issue. Pinging via IP address worked fine.
I have discovered that the response of 198.18.1.1 is coming from a broadband router that is on the wan interface but doesn't have an upstream connection yet - if I send DNS requests to the router IP then it returns 198.18.1.1 for everything. This interface is 2nd in priority on the failover list, and it is turned off in the failover list. The primary connection is mob1s1a1. I have manually configured DNS on mob1s1a1 and wan to 22.214.171.124, 126.96.36.199 but the local DNS resolver on the RUTX router still seems to be forwarding queries to the broadband router that has been assigned via DHCP.
Is there a DNS forwarding address that is configured at a higher level than the WAN interfaces? How can I stop the router using this DHCP-assigned address? Looking in /etc/config/network shows "option peerdns 0" for both interfaces.
I understand the best way to fix this would be to have a broadband router that doesn't return junk results when it has no connection to the internet (though I think if the DNS forwarding address doesn't follow whatever connection is online in the failover settings it would send requests that timed out), but it's ISP equipment and seeing this strange failure mode is helpful to find out and work around before we go live on this location.