In a recent article titled “What came first- the CNAME or the A record?” Cloudflare explains how an unclear RFC specification caused the popular Cloudflare’s 1.1.1.1 service to break. After identifying the breakage and the ambiguity in older DNS standards regarding record order, Cloudflare proposes a clarified specification.
On January 8, a routine update to the DNS service changed the order in which CNAME records appeared in responses, causing some DNS clients to fail when resolving names because they expected the alias records to come first. While most modern software treats the order of records in DNS responses as irrelevant, the Cloudflare team found that some implementations expect CNAME records to appear before all other record types.
When that order…