DNS Connects Names To Services
DNS translates names such as example.com into technical destinations such as IP addresses and mail servers. Without DNS, visitors would need to remember server addresses.
Common Record Types
- A: points a hostname to an IPv4 address.
- AAAA: points to an IPv6 address.
- CNAME: aliases one hostname to another.
- MX: identifies mail servers.
- TXT: stores verification and email-policy information.
- NS: identifies authoritative nameservers.
Why Changes Are Not Instant Everywhere
Resolvers cache DNS answers to reduce load and improve speed. The TTL value tells resolvers how long they may keep a cached answer. Until the cache expires, some visitors may continue seeing the old destination.
Propagation Is Really Cache Expiration
People often call this delay propagation, but the change does not slowly travel in one direction. Different resolvers refresh at different times.
Nameserver Changes Can Take Longer
Changing authoritative nameservers affects how the entire DNS zone is located. Existing delegation information and cached records may remain active for a while.
Plan Changes Carefully
Lowering TTL values before a migration can reduce the time old records remain cached. Do this early enough for the previous TTL to expire before the planned change.
How To Check DNS
Use DNS lookup tools to compare A, MX, TXT, and NS records. Remember that your local computer may show a cached result even when another resolver has updated.