OPT

networking

Stands for: Option (pseudo-record)

A pseudo-record that carries EDNS options in a DNS message.

The OPT record (RFC 6891) is not a real resource record but a container in the additional section that carries EDNS metadata like buffer size and flags. dig shows it as the OPT pseudo-section.

The OPT record is the container EDNS uses, a pseudo-record that appears in a DNS message's additional section and never exists in a zone. It advertises the sender's supported message size and carries option codes for extensions.

The reason it is worth knowing separately is diagnostic. Packet captures of DNS problems frequently show an OPT record with a buffer size that does not match what the path can carry, which produces truncation and retry behaviour that looks like intermittent failure. Lowering the advertised size is a standard workaround for a path that fragments badly, and recognizing OPT in a capture is what turns an unexplained DNS slowdown into a specific and fixable path MTU issue.

Also known as: opt

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