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Malformed packets from 127.0.0.1 every ~62.5 seconds

Posted on 2016-09-19
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Last Modified: 2016-10-09
On a 2008r2 Domain Controller, with Exchange Exchange 2010 installed (I am very aware that this is not optimal, but when you inherit a client network...)

Event ID 5502 repeated every ~62.5 seconds with the text

The DNS server received a bad TCP-based DNS message from 127.0.0.1.  The packet was rejected or ignored. The event data contains the DNS packet.

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As Wireshark is unable to capture from loopback, I used RawCap  to capture traffic on the loopback interface for several minutes, and then opened up the capture in WireShark, which shows a repeated malformed packet as per the attached.

While I have stopped the event from showing by changing DNS event logging from "All events" to "Errors and warnings", I am interested in why might be causing this, especially with the frequency of recurrence...
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Question by:ArneLovius
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4 Comments
 
LVL 62

Expert Comment

by:gheist
ID: 41806861
Is it some montiring script checking DNS is up with TCP? like nagios/zabbix whatever?
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Author Comment

by:ArneLovius
ID: 41806989
I haven't found anything obviously scheduled, and as the source is 127.0.0.1 it has to be local to the server.

The cycle time of ~62.5 seconds makes me think that its an internal process rather than a scheduled one, but I'm quite happy to admit that I;m stumped by it :-)
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Accepted Solution

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gheist earned 2000 total points (awarded by participants)
ID: 41807346
nslookup timeout is 2s. so something sleeps 1min, then does nslookup then sleeps again.
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LVL 62

Expert Comment

by:gheist
ID: 41835700
Hard to guess better.
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