DNSTOP(8) | System Manager's Manual | DNSTOP(8) |
dnstop
— displays
various tables of DNS traffic on your network
dnstop |
[-46apsQR ] [-b
expression] [-i
address] [-f
filter] [-r
interval] [device]
[savefile] |
dnstop
is a small tool to listen on
device or to parse the file
savefile and collect and print statistics on the local
network's DNS traffic. You must have read access to
/dev/bpf*.
The options are as follows:
-4
-6
-Q
-R
-a
-b
expression-i
address-p
-r
-l
levelFor 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.
-f
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 REFUSED.
The "qtype-any" filter tells
dnstop
to count only message of type ANY.
-n
name-P
-B
buckets-X
pcap
formatWhile running, the following options are available to alter the display:
If stdout is not a tty, dnstop
runs in
non-interactive mode. In this case, you must supply a savefile for reading,
instead of capturing live packets. After reading the entire savefile,
dnstop
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, dnstop
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
and -Q
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.
21 March, 2008 | Debian |