[Snort-users] snort inline (non-drop mode) br0

Lawrence R. Hughes, Sr. lhughes at ...14822...
Tue Feb 1 15:42:56 EST 2011


Sorry If I did not provide the info you need.here it is: snort  

 We are experiencing a large percentage of dropped packet. dropped packets start very low, but on the increase all the time exceeding 70%. please see attached startup and  perf. monitor report

2.       We see a large number of open sessions  without any reduction.  see attached perf. monitor  and attached config file

3.       Only 7 rule groups are applied

4.       We have disabled many preprocessors and so rules in an attempt to debug the dropped packet problem??

5.       We do not detect duplicate traffic, snort is running on BR0 which is made of eth0 and eth1.

6.       Snort is not on a network tap.running inline without blocking.

7.       We are detecting alerts which are valid alerts.

8.       Machine is duel core, 16GB memory @1333Ghz, fSB 1333Ghz, nic on PCI 2.0 5GBs, Raid SAS 15000RPM


The issue is the dropped packets...i hope the attached files provide you with enough info to be able to help



  ----- Original Message ----- 
  From: Joel Esler 
  To: Lawrence R. Hughes, Sr. 
  Cc: snort-users at lists.sourceforge.net 
  Sent: Tuesday, February 01, 2011 1:45 PM
  Subject: Re: [Snort-users] snort inline (non-drop mode) br0


  I keep seeing you post to the list asking about open sessions.  But I never see any responses to anyone's questions that we ask.

  Are you having a problem with open sessions, or are you perceiving it to be a problem?  What's the problem?  Are you dropping packets?  Are you seeing duplicate traffic?

  Is Snort not detecting things?  What's the issue?


  On Tue, Feb 1, 2011 at 12:59 PM, Lawrence R. Hughes, Sr. <lhughes at ...14895...2...> wrote:


    We use snort inline in the non-drop mode and our sensor is listens on br0.
    Could it be that we detect the 3whs (session) with stream5, but don't detect when the session has ended, thus giving us a high rate of open sessions?

    If this is the case, then what interface would be better to use eth0 or eth1 (currently both eth0 & eth1 are configed to give us br0) ?


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  Joel Esler
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