What is a “[P2P0]WARNING: no two valid MoneroPulse DNS checkpoint records were received” warning?

Question

At the end of synchronization I saw this error:

[P2P0]WARNING: no two valid MoneroPulse DNS checkpoint records were received

I noticed no effect on the functionality of the daemon or the wallet, but am curious about what it means.

Answer 1

This was explained by Fluffypony on Reddit:

It says "warning", so it's not an error, it's just a notice:)

MoneroPulse is informational only, unless you're running an unmanaged node and you've thus set the flag to explicitly follow MoneroPulse checkpoints. Currently there are three things to note with MoneroPulse:

1. moneropulse.co is having issues, it's in the process of being moved to a different registrar. BUT moneropulse.org, moneropulse.net, and moneropulse.se are all fine and pass DNSSEC validation, so finding 2 working ones is not that hard.

2. We're having issues with our baked-in root trust anchor for systems that don't have trust anchors. You may have noticed a message on startup complaining about "unsupported algorithm for trust anchor . DNSKEY IN" - we have a new format for the baked-in anchor that should fix this, but it's not part of 0.9 or 0.9.1.

3. Even if 1 and 2 are perfect and resolved there are some ISPs that run DNS servers that don't acknowledge the +dnssec flag when making requests, so there are some environments where you're never going to get a valid MoneroPulse response. That's why MoneroPulse is just informational only:)

Answer 2

To fix this use Google or Cloudflare DNS servers instead of your ISP ones:

Google DNS:

DNS_PUBLIC=tcp://8.8.8.8 ./monerod

Cloudflare DNS:

DNS_PUBLIC=tcp://1.1.1.1 ./monerod

Obviously, you can also set Google or Cloudflare DNS servers system wide in your network configuration.