dnstracer
trace a chain of DNS servers to the source
TLDR
Find out where your local DNS got the information on www.example.com
Start with a [s]pecific DNS that you already know
Only query IPv4 servers
Retry each request 5 times on failure
Display all steps during execution
Display an [o]verview of all received answers after execution
SYNOPSIS
dnstracer [options] name
DESCRIPTION
dnstracer determines where a given Domain Name Server (DNS) gets its information from, and follows the chain of DNS servers back to the servers which know the data.
Options are:
- -c
Disable local caching.
- -C
Enable negative caching.
- -e
Disable EDNS0 options.
- -E size
Set EDNS0 size, default is 1500 bytes.
- -o
Enable overview of received answers at the end.
- -q queryclass
Change the query-class, default is A. You can either specify a number of the type (if you're brave) or one of the following strings: a, aaaa, a6, soa, cname, hinfo, mx, ns, txt and ptr.
- -r retries
Number of retries for DNS requests, default 3.
- -s server
DNS server to use for the initial request, default is aquired from the system. If a dot is specified (.), A.ROOT-SERVERS.NET will be used.
- -v
Be verbose on what sent or received.
- -4
Use only IPv4 servers, don't query IPv6 servers (only available when IPv6 support hasn't been disabled)
- -S sourceaddress
Use this as source-address for the outgoing packets.
HOW IT WORKS
It sends the specified name-server a non-recursive request for the name.
Non-recursive means: if the name-server knows it, it will return the data requested. If the name-server doesn't know it, it will return pointers to name-servers that are authoritive for the domain part in the name or it will return the addresses of the root name-servers.
If the name server does returns an authoritative answer for the name, the next server is queried. If it returns an non-authoritative answer for the name, the name servers in the authority records will be queried.
The program stops if all name-servers are queried.
Make sure the server you're querying doesn't do forwarding towards other servers, as dnstracer is not able to detect this for you.
It detects so called lame servers, which are name-servers which has been told to have information about a certain domain, but don't have this information.
EXAMPLES
Search for the A record of www.mavetju.org on your local nameserver:
dnstracer www.mavetju.org
Search for the MX record of mavetju.org on the root-nameservers:
dnstracer -s . -q mx mavetju.org
Search for the PTR record (hostname) of 212.204.230.141:
dnstracer -q ptr 141.230.204.212.in-addr.arpa
And for IPv6 addresses:
dnstracer -q ptr -s . -o 2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.6.4.0.2.0.0.0.0.8.b.0.e.f.f.3.ip6.arpa
SEE ALSO
ntptrace (8), traceroute (8), dig (1)
AUTHOR
Edwin Groothuis, edwin@mavetju.org (http://www.mavetju.org)
See http://www.mavetju.org/contacts.php for mailing-lists.
