Monday, July 26, 2010

FreeBSD dnstracer command description


鈼?Name
dnstracer - trace a chain of DNS servers to the source

鈼?Description
dnstracer dns server can determine where to obtain authoritative DNS records, and displays.

鈼?works
dnstracer through the first set dns server, send the name of non-recursive queries.

Non-recursive query: check if the dns server to know the results, then return information.
Does not know the exact results will be closer to the target server dns.

If the dns servers respond to authoritative answer, then the server is queried next.
If the dns server to respond to non-authoritative answer, you may be in accordance with the target server to respond to inquiries.

dnstracer this program, all the authoritative dns server in the query results and stop.

Please confirm your initial query dns server does not forward the query to other dns servers.
dnstracer will not find such a change.

dnstracer will detect those with the wrong dns server. (who should have a dns record, but not the server.)

鈼?Installation (2004 Note: the path / usr / ports / dns / dnstop)

鈼?syntax dnstracer [options] name

鈼?parameters
-C Cancel the cache local records.

-O in dnstracer produce an overview of the last record.

-Q queryclass change the query class, the default is class A.
The following class can use a, aaaa, a6, cname, hinfo, mx, ns, txt.

-R retrIEs check fails, re-check the number of times. (Default is 3 times)

-S server Set the original query dns server issue. (The default is the system's dns server)
If using. Is that the use of A.ROOT-SERVERS.NET

-T timeout waiting for response time (timeout). The default is 15 seconds

-V verbose mode is used.

鈼?example
A: to B.ROOTSERVERS.NET for the first server to query the authoritative DNS server ohaha.ks.edu.tw.
# Ndstracer-s B.ROOTSERVERS.NET ohaha.ks.edu.tw
A cache server can be seen moesun.edu.tw situation. Figure:


B: to B.ROOTSERVERS.NET for the first server to query the authoritative DNS server ohaha.ks.edu.tw. But with the-c parameter, clear the cache.
# Ndstracer-c-s B.ROOTSERVERS.NET ohaha.ks.edu.tw
The cache can be the original moesun.edu.tw resolve the situation out. Figure:

C: Lame Server (which should have a dns record, but not the server.)






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