DNS TTL Limits at Public DNS Resolvers

In my post about the basics of DNS TTLs and caching I mentioned that DNS resolvers use the TTL of the record to determine how long to cache any particular record for. While this is /normally/ true, there are exceptions. Namely, certain public DNS resolvers have a upper limit of the TTL that they will cache. That is, if you set a TTL longer than their limit, the resolver will bring the TTL down to their limit and cache it using their TTL.

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Understanding DNS: Common Record Types

In my last post in this series I talked about authoritative nameservers and what they do. Their function is responding to queries for domain names they are authoritative for. These queries are for specific record types; in this post I will be talking about common record types you will encounter in your use of the DNS.

For the sake of simplicity and ease of understanding I’m limiting this post to the most common record types i.e records you are most likely to encounter and use in your day-to-day use of the DNS. These are not all the record types that are available for use in the DNS.

Let’s get started.

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