Pace router not handling DNS over TCP

[jnmoyne]

I have my Sonic router configured for automatic DNS, machines on the LAN get their DNS from DHCP therefore have the router as the DNS server. From the LAN, when trying to resolve a particular DNS entry the UDP reply is truncated so the resolver switches to TCP DNS... and that port is not even open on the router, therefore the request fails.

It's a problem with the Sonic router itself not being able to handle DNS over TCP because if I send the DNS request to the DNS server the router itself got from the WAN (208.201.224.11) then it works.

What are my options (besides having to set the DNS servers manually on my LAN machines)? Set the the router with static DNS IPs (and hope in that case it will not still want to act as a proxy DNS server...)?

[sysops]

I found this same issue a while back and can confirm it's a real thing. The Pace doesn't listen on TCP port 53 and therefore doesn't proxy DNS over TCP. I recall having Sonic change the DHCP DNS servers from the Pace CLI (can't do it in the GUI) but that didn't help since it still wanted to proxy things.

Lucky for us the site who's DNS response was truncated and served over TCP shortened things up so it'd fit in UDP and this was no longer an issue. In the interim we just set DNS manually on each PC which comes with it's own set of issues, especially on laptops that moved in and out of Sonic's network.

I think your options may be limited, though my friend in SF who just got fiber got a new device that isn't a Pace modem so you may wanna inquire about one of those (no clue if it has this same issue or has a way around it).

[jnmoyne]

Thanks for confirming the problem, I'm a new customer (fiber in SF) and my service came with a Pace router. Will try to contact Sonic support more directly about this (I thought these forums where the right place for my question, I guess they are not really monitored by Sonic support then...)

[jnmoyne]

Update: so I received a Smart/RG router box to try from Sonic, but same thing it also does not handle DNS over TCP proxying. So I am left with the only option of using my own router, which does handle DNS over TCP requests with no problem.