How to Fix: ssh to fqdn with private aaaa record returns "Undefined error: 0" on ipv4 only internet

The issue of ssh connecting to fqdns with private aaaa records returning 'Undefined error: 0' on ipv4 only internet is a known limitation that affects users who have set up yggdrasil networks with ipv6 only connectivity. This error occurs when the ssh client attempts to connect to a host with an ipv4 address, but the dns resolution for that address fails.

This issue can be frustrating as it prevents users from establishing secure connections to hosts within their private ipv4 network. Fortunately, there are workarounds and fixes available to resolve this problem.

⚠️ Common Causes

• The primary reason why this error occurs is due to the way ssh handles dns resolution for ipv4 addresses. When a user attempts to connect to an ipv4 address using the ssh -6 option, the client will first attempt to use ipv6 dns resolution. However, if the dns server returns no response or an invalid ipv6 address, the client will then fall back to ipv4 dns resolution, which can be unreliable in this case.
• Another possible cause is related to the way Cloudflare handles aaaa records for private networks. In some cases, the aaaa record may not be propagated correctly to all dns resolvers, leading to an invalid dns response and resulting in the 'Undefined error: 0' message.

✅ Best Solutions to Fix It

✨ Wrapping Up

In conclusion, the issue of ssh connecting to fqdns with private aaaa records returning 'Undefined error: 0' on ipv4 only internet can be resolved by enabling ipv4 fallback for ssh or configuring Cloudflare dns settings. By following these steps, users should be able to establish secure connections to hosts within their private networks using ipv4 addresses.