Deny TCP (no connection) flags RST on inside intf ? PIX 6.3.5


I have recently moved from a "managed" firewall to a pix running 6.3.5; and in the syslogs I'm seeing enough of the following messages that I'm concerned that I have a timeout, etc. misconfigured on the pix.

08:01:53 Local4.Info Apr 14 2006 12:01:36: %PIX-6-302013: Built outbound TCP connection 17848999 for outside: ( to inside: (

08:01:53 Local4.Info Apr 14 2006 12:01:36: %PIX-6-302014: Teardown TCP connection 17848999 for outside: to inside: duration 0:00:01 bytes 294 TCP FINs

08:01:53 Local4.Info Apr 14 2006 12:01:36: %PIX-6-106015: Deny TCP (no connection) from to flags RST ACK on interface inside

08:01:53 Local4.Info Apr 14 2006 12:01:36: %PIX-6-106015: Deny TCP (no connection) from to flags RST on interface inside

I would expect these more on the outside intf where the pix shuts down a connection more quickly than the web server can react; but I don't understand them on the inside.

There are usually several series of these log enties in a row - sometimes a up to 15, but often only 4 or 5. I have compared both the originating hosts and the destination hosts over several days and they're apparently random hosts browsing random internet servers - I can find no pattern except a large number of the above log entries.

The durations are always short for these session - and over a "series" of these entries the source port number (client browser) generally increments by one - but even this isn't constant.

This is the only route to the Internet for these hosts.

Can someone please help me understand these entries?

Many thanks, Nick

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Loading thread data ...

PIX questions are better addressed to -- there are more PIX people there.

Normal message.

Normal message.

The same thing can happen: the outside host can shut down the connection faster than the inside reacts.

The problem started in PIX 6.2(2) or so: the PIX no longer holds on to connection information for a few seconds to check for trailing packets from a connection winding down.

Notice that the first of the messages was RST ACK: that implies that the other end sent a RST. The PIX closed the connection then, and the RST ACK sent by the inside host is being logged. Then the inside host closes the connection from its end, generating a RST of its own.

You might be able to play with the "timeout" parameters, but I don't think it will help.

Reply to
Walter Roberson

Thank you Walter - and I appreciate your advice to use the in the future.


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