displays various tables of DNS traffic on your
is a small tool to listen on
or to parse the file
and collect and print statistics on
the local network's DNS traffic. You must have read access to
The options are as follows:
- count only messages with IPv4 addresses
- count only messages with IPv6 addresses
- count only DNS query messages
- count only DNS reply messages
- anonymize addresses
- BPF filter expression
(default: udp port 53)
- ignore select addresses
- Do not put the interface into promiscuous mode.
- Redraw interval (seconds).
- keep counts on names up to
level domain name levels.
For example, with -l 2 (the default), dnstop
will keep two tables: one with top-level domain names, and another with
second-level domain names. Increasing the
level provides more details, but also
requires more memory and CPU.
- input filter name
The "unknown-tlds" filter includes only queries for TLDs that are
bogus. Useful for identifying hosts/servers that leak queries for things
like "localhost" or "workgroup."
The "A-for-A" filter includes only A queries for names that are
already IP addresses. Certain Microsoft Windows DNS servers have a known
bug that forward these queries.
The "rfc1918-ptr" filter includes only PTR queries for addresses
in RFC1918 space. These should never leak from inside an organization.
The "refused" filter, when used with the
-R option, tells
dnstop to count only replies with rcode
The "qtype-any" filter tells dnstop
to count only message of type ANY.
- Only count messages within the domain
- Print "progress" messages on stderr when in
- Use buckets hash table
- Do not tabulate the sources + query name counters. This can
significantly reduce memory usage on busy servers and large
- a captured network trace in
- ethernet device (ie fxp0)
While running, the following options are available to alter the display:
- display the source address table
- display the destination address table
- display the breakdown of query types seen
- display the breakdown of response codes seen
- display the breakdown of opcodes seen
- show 1st level query names
- show 2nd level query names
- show 3rd level query names
- show 4th level query names
- show 5th level query names
- show 6th level query names
- show 7th level query names
- show 8th level query names
- show 9th level query names
- show sources + 1st level query names
- show sources + 2nd level query names
- show sources + 3rd level query names
- show sources + 4th level query names
- show sources + 5th level query names
- show sources + 6th level query names
- show sources + 7th level query names
- show sources + 8th level query names
- show sources + 9th level query names
- reset the counters
- exit the program
If stdout is not a tty, dnstop
non-interactive mode. In this case, you must supply a savefile for reading,
instead of capturing live packets. After reading the entire savefile,
prints the top 50 entries for each table.
By default dnstop
examines only query messages and
ignores replies. In this case the response code table is meaningless and will
likely show 100% "Noerror."
If you supply (only) the -R
command line option,
examines replies and ignores queries. This
allows you to see meaningful response code values, as well as all the other
tables. In this case all the query attributes (such as type and name) are
taken from the Question section of the reply.
Note, however, that it is common for a stream of DNS messages to contain more
queries than replies. This could happen, for example, if the server is too
busy to respond to every single query, or if the server is designed to ignore
malformed query messages. Therefore, you might want to examine both queries
and replies by giving both -R
command line options. In this case, only the
response code counts are taken from the replies and all other attributes are
taken from the queries.
Does not support TCP at this time.