Re: How to force recursions to TCP only

Kevin, you're right that there's no option. But blocking UDP in the
firewall isn't going to fly, the recursor only falls back to TCP on
TC=1 (truncated) answers, not on UDP timeout or error.

In general it's a bad idea to force TCP, as it increases load on both
recursor and authoritative servers. Better fix your UDP connectivity.

	-Otto


On Fri, Feb 28, 2025 at 09:10:59AM -0500, Kevin P. Fleming via Pdns-users wrote:

> I don't think there are any configuration options in the recursor do to this, so you'll have to do it in a firewall system outside of the recursor. Blocking all outbound traffic to UDP port 53 would take care of it.
> 
> On Fri, Feb 28, 2025, at 06:45, Carlos N via Pdns-users wrote:
> > Hello all
> > 
> > I,m looking for a way of forcing all outgoing queries from recursor to authoritative servers to be TCP.
> > I'm experiencing some packet discards in my platform internal network and i think forcing to TCP may help overcome some of the problems caused by discards.
> > Does anybody know how to do this or if it is even possible.
> > Documentation doesn't give any clue.
> > Kind regards and thanks in advance.
> > 
> >      Carlos
> > 
> > 
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> > 

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