DNS propagation: why a domain stops working after an NS change

After changing DNS records or name servers, a domain does not immediately switch to the new configuration. DNS servers around the world cache responses and update them at different speeds. The period during which all servers transition to the new data is called propagation.

You can check the current DNS status from different servers using DNS Lookup on rechecker.ru.

How DNS caching works

1. The user requests example.com
2. The resolver (the provider, Google 8.8.8.8, etc.) checks its cache
3. If the record exists and its TTL has not expired, the cached value is returned
4. If not, the query goes to the authoritative NS, and the response is cached for the TTL period

Until the TTL expires, the old data continues to be returned. Propagation is the process by which all resolvers gradually receive the updated records.

Factors that affect propagation time

TTL (Time To Live)

The record's lifetime in seconds. A DNS server caches the response for this period.

The higher the TTL was before the change, the longer the old data may remain in the cache. Recommendation: reduce the TTL to 300–600 24–48 hours before the change.

DNS hierarchy

A query follows this chain: root → TLD (.com) → the domain's authoritative NS. Each level may cache the response. TLD-zone NS records (.com, .ru) are cached for 24–48 hours by many providers.

Changing an NS vs. changing an A record

When NS changes, the authoritative server changes. Until TLD servers update their cache of NS records, queries go to the old NS.

NS change: step-by-step plan

1. Preparation (24–48 hours in advance)

• Create a zone on the new NS with the required records
• Make sure A, MX, TXT, etc. are configured correctly
• Check availability by querying the new NS directly:

dig @ns1.new-host.com example.com

2. Lowering the TTL

On the old NS, reduce the TTL for critical records to 300–600. This will speed up the update after the change.

3. Changing NS at the registrar

In the registrar's control panel, enter the new NS (ns1.new-host.com, ns2.new-host.com, etc.). Save the changes.

4. Waiting

Usually 24–72 hours. In rare cases, up to 48 hours. Check from different servers.

5. Checking propagation

dig @8.8.8.8 example.com NS
dig @1.1.1.1 example.com NS
dig example.com A

Online: DNS Lookup — check from different DNS servers.

Changing an A record (without changing NS)

This is simpler: only the A record value on the authoritative NS changes. Resolvers will update their cache after the TTL expires.

Recommendation: reduce the TTL to 300 a day before the change. After the change, wait 1–2 TTLs and, if necessary, restore the TTL to 3600–86400.

Changing hosting (same NS)

If the NS does not change (for example, if you use your hosting provider's DNS), you only need to update the A record to the new IP. Propagation depends on the TTL.

Problems during propagation

Website unavailable

• Make sure the zone is configured on the new NS and returns an A record
• Check that the domain's NS servers actually point to the new hosting provider

Email is not being delivered

• MX records must be on the new NS
• SPF, DKIM, and DMARC must be on the new NS

Different results from different servers

This is normal during propagation. Some resolvers have already updated; others have not. Wait, or clear the local DNS cache (if you are testing from your own server).

Speeding up propagation

It cannot be fully accelerated—the caches are controlled by providers. You can:

1. Lower the TTL in advance
2. Update the zone on the old and new NS at the same time (to avoid a gap)
3. Use services with a short TTL (for example, Cloudflare)

Checking from different servers

dig @8.8.8.8 example.com +short
dig @1.1.1.1 example.com +short

If the results differ, propagation is still in progress.

Recommendations

• Do not schedule an NS change for Friday—weekends make support more difficult
• Keep the old zone working for 72 hours after the change
• Guide to record types: DNS records: A, AAAA, CNAME, MX, TXT — a complete guide