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Date:      Mon, 19 Jan 2009 10:44:12 -0800
From:      Doug Hardie <bc979@lafn.org>
To:        freebsd-questions@freebsd.org
Subject:   Port 7070
Message-ID:  <8904C35C-EDFE-419D-989E-84F20A364DD4@lafn.org>

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I just ran a netcat (nc -z) on my production servers and found an  
unusual response:

Connection to xxxx 7070 port [tcp/arcp] succeeded!

I checked on all my production and test servers (7.0 stable as of  
quite some time ago) and got the same response.  I can't figure out  
why that port is open.  It always returns a reset when a connection is  
opened.  netstat -an does not return any 7070 entries.  sockstat does  
not show any 7070 entries.  There is no 7070 entry in /etc/services.   
ktrace of inetd shows nothing.  tcpdump on the server shows the SYN  
and RST packets only.  tcpdump on the client machine shows a complete  
TCP negotiation completion followed by a termination.  The client is  
going across the internet.

Running the client on a machine on the servers LAN shows that the port  
is not open.  And tcpdump from both shows only a SYN followed by a  
RST.  This indicates that some router between the original client and  
the servers is accepting the connection and then forwarding it on.   
This doesn't happen on other ports (although there may be a couple  
others I haven't chased down yet though).  The only router we have in  
the path is a Cisco 2501 running a 2000 vintage IOS with nothing like  
that in its configuration.  Its a simple pass everything through  
setup.  Any ideas what is happening here?



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