Hi team,

I've been investigating DNS propagation behavior across European resolvers and wanted to share some observations that might be useful to the group.

When testing DNS record changes (particularly A, AAAA, and MX records) across resolvers in different RIPE member regions, I've noticed significant inconsistencies in how quickly changes propagate — even when TTLs are identical. Some examples:

• Records with TTL 300 updated within 5 minutes on Cloudflare (1.1.1.1) and Google (8.8.8.8), but took 15-25 minutes on several ISP resolvers in DE, NL, and FR.
• CNAME chains with 3+ levels caused noticeably slower propagation compared to direct A records, particularly on resolvers that don't support aggressive NSEC caching (RFC 8198).
• Some ISP resolvers appear to enforce a minimum TTL floor (often 300-600s), overriding the authoritative server's lower TTL values.

For anyone investigating similar behaviour, I've found it helpful to query the same record from multiple global locations simultaneously to identify which resolvers are lagging. We built a tool called DNS lookup that does this at it queries from 20+ server locations in parallel and shows per-location results with response times.

Has anyone else on the list observed ISP resolvers in the RIPE region enforcing minimum TTL values? RFC 8767 (Serving Stale Data) seems related, but I'm curious whether this is intentional policy or just aggressive caching implementations.

Regards,

Vahid