[Pdns-users] Slow query and SERVERFAIL from local pdns_recursor

[Thomas Mieslinger]

On 9/10/20 3:40 PM, Christian Degenkolb wrote:
> what is a reasonable low value for udp-truncation-threshold? I tried
> with 900 and 600 (as low as half the default value) but found no
> improvements.

I use 1220 because the always recommended 1232 does not work for me with
IPv6.

Some months ago the network team forgot to configure fragment handling
correctly on JunOS. As soon as I lowered the udp-truncation-threshold
dhl.com and others started working immediately.

> Also I don't think this is a vmware.com problem since I have the same
> problem with multiple domains.

Another thing that I noticed is that not well utilized recursors perform
bad because they need to work through the whole chain from . to the
zones nameserver including many extra queries for dnssec.

"not well utilized" as in less than 10k queries/second.

Please try to "preheat" your recursor and see what changes. For use at
home I've written https://github.com/miesi/DNS-Standheizung to have all
tld namesserver with their A/AAAA/... in the recursors chache

Cheers

Thomas