dnstrace

## Name

dnstrace — diagnose DNS query resolution problems

## Synopsis

`dnstrace` {`t`} {`fqdn`} {`s`...}

## Description

dnstrace searches for all DNS servers that can affect the resolution of records of type `t` under the domain name `fqdn`, starting from the root content DNS server(s) `s`.

It uses the standard DNS resolution algorithm, but follows all possible paths in the algorithm. It prints all responses it receives from content DNS servers; it also prints warnings about slow servers, dead servers, misdelegated ("lame") servers, and misformatted packets.

Beware that complete traces are large and incur non-trivial network traffic. As of January 2001, dnstrace produces more than 5 megabytes of output for the complete trace of `cr.yp.to` starting from all of the root servers. It ends up sending more than 6000 queries to more than 200 different servers.

The output of dnstrace is machine-parseable. To convert it to human-readable form, pass it through dnstracesort(1).

## History

dnstrace was originally part of Daniel J. Bernstein's djbdns toolset in 2000.

## Author

Original code and documentation by Daniel J. Bernstein. Documentation modernizations by Jonathan de Boyne Pollard.