How ALIAS Records Resolve with Secondary DNS

DNSimple ALIAS records provide dynamic resolution for apex domains. When secondary DNS servers pull your zone from DNSimple over AXFR, ALIAS cannot be transferred as a standard record type. DNSimple resolves each ALIAS to A and AAAA addresses, then transfers those addresses to your secondary servers.

The challenge with secondary DNS and ALIAS records

Traditional records such as A, MX, or TXT are static and transfer directly during AXFR. An ALIAS record is virtual: DNSimple looks up the target in real time and returns A or AAAA answers.

Because ALIAS is not a transferable standard type, DNSimple cannot send the ALIAS rule itself. It resolves the ALIAS to IP addresses and transfers those resolved records instead.

How DNSimple keeps secondary servers up to date

When you configure outbound secondary DNS (DNSimple as primary) for a zone that has ALIAS records, DNSimple:

1. Resolves ALIAS records at setup - Writes the resulting A and AAAA records into the zone transfer data that secondaries pull.
2. Re-resolves when the TTL expires - Checks each zone every few minutes and re-resolves its ALIAS records once the shortest ALIAS TTL in that zone has elapsed. A lower TTL on your ALIAS record means more frequent refreshes.
3. Updates transfer data - Removes stale A and AAAA addresses for that ALIAS and writes the new ones.
4. Sends NOTIFY - Sends a NOTIFY message to configured secondary name servers so they can start a new AXFR or IXFR and pick up the updated addresses.

This keeps secondary servers aligned with the latest ALIAS resolution while you use secondary DNS for redundancy. See Add a secondary DNS server to DNSimple and DNS Redundancy Options at DNSimple.

Have more questions?

If you have questions about ALIAS records and secondary DNS, contact support, and we’ll be happy to help.