topic Rate Limiting DNS Queries in Full Fibre

Rate Limiting DNS Queries

hoolieco — Fri, 28 Feb 2025 15:35:17 GMT

Without getting overly technical, I was wondering if Plusnet limits the number of DNS queries outbound on the line

I have a pfsense setup and have the Resolver set to recursive mode. It goes out regularly and keeps my local DNS up to date leading to a quicker response in the longer term on the network

I've noticed that I've been getting some of err_no_response from my full fibre 900 line and the solution has been to switch to forwarding over DNS over TLS on port 853 where the problem has stopped.

Anyone got any ideas?

Re: Rate Limiting DNS Queries

outcast — Fri, 28 Feb 2025 19:48:45 GMT

When I was with Plusnet and running pfSense, I would regularly review all the available options for DNS, benchmarking them using https://www.grc.com/dns/benchmark.htm , and choosing the fastest responders and keeping a lookout for those DNS that occasionally failed to respond. It was noticeable that the Plusnet DNSs FREQUENTLY showed failed lookups, whereas the other public DNSs usually were error free.

This was BEFORE Plusnet moved to a new DNS platform in July 2023, and I left Plusnet soon after so don't know whether the new platform fixed the underlying DNS unreliability, and I'd given up using Plusnet DNS years ago anyway.

@hoolieco wrote:
...I was wondering if Plusnet limits the number of DNS queries outbound on the line

I very much doubt it, my experience is that they were just flaky (whether that's the DNS server or the DNS load balancers).

Why would you want to use Plusnet DNS anyway ?, other DNS such as Quad9 or OpenDNS provide better results, have optional desirable security features, and are not subject to the same level of monitoring and censorship that you get with BT group companies.

Re: Rate Limiting DNS Queries

hoolieco — Fri, 28 Feb 2025 23:03:56 GMT

Hi there. Thanks for the response. I was doing full resolution through the authoritive servers instead of any one DNS and if I'm using one it's either quad 9 or open DNS when doing forwarding.

That's the crux of it all, by reverting to using quad 9 as a forwarder through TLS, the issues stopped.

When using unbound on pfsense, I set it so it kept the cache fresh and it automated requeried DNS records about to expire their TTL and in some cases i could see 80 to 90 outbound port 53 queries at once.

It's that burst of queries that made me think Plusnet was restricting my connection to protect itself.

Re: Rate Limiting DNS Queries

hoolieco — Sat, 01 Mar 2025 13:40:34 GMT

Turns out with pfsense DNS resolver, I was fragmenting my DNS packets. Setting edns buffer size in advanced settings to 1232, worked with my full fibre line. Now I get no resolution issues and it's fully recursive. No public or Plusnet DNS needed.

Re: Rate Limiting DNS Queries

outcast — Sat, 01 Mar 2025 16:02:56 GMT

@hoolieco wrote:

... Setting edns buffer size in advanced settings to 1232, worked ...

What size did you previously have it set to ?

It appears that the default value was set to 1232 five years ago in pfSense 2.4.5

Re: Rate Limiting DNS Queries

hoolieco — Sun, 02 Mar 2025 14:11:36 GMT

Auto. I can't remember if I set it or it's default on 2.7.2.
Either way, it's sorted.

Thanks for your input.