[Snort-users] snort dropping 48%

Sheahan, Paul Paul.Sheahan at ...2218...
Thu May 6 11:04:03 EDT 2004


I still don't have an answer either. 49% of packets being dropped is
absolutely ridiculous.

I recently ran TOP to check memory while Snort was running my
content-based rules and noticed that even though I had 1 gig of ram in
my server, there was almost no free memory. So I upgraded to 4 gig of
RAM figuring Snort just needed more RAM, but the same problem is still
occurring, 49% of packets are still being dropped.

Should I take a look at libpcap? I understand there are multiple
versions. What version should I be running?

Thanks


-----Original Message-----
From: snort user [mailto:snortuser at ...125...] 
Sent: Wednesday, May 05, 2004 1:42 PM
To: Sheahan, Paul
Subject: RE: [Snort-users] snort dropping 48%

Im actually getting the same problem on a Debian machine. When the
traffic 
exceeds 100Mb/s snort really starts dropping packets fast. If I remove 
content based rules then dropped apckets significantly drop. I never saw
a 
reply other than it could be a RedHat problem so I was wondering if
anyone 
else had any ideas since I am not on RedHat.


>From: "Sheahan, Paul" <Paul.Sheahan at ...2218...>
>To: <snort-users at lists.sourceforge.net>
>Subject: [Snort-users] snort dropping 48%
>Date: Wed, 28 Apr 2004 13:46:55 -0400
>
>Can anyone give me a tip in this situation?
>
>
>
>I used to have a Snort 1.9 sensor running on RHLinux7 on a 100mb
>Ethernet network. On that sensor I ran the most of the default rules
>plus my own custom rule file, which contained a lot of content-based
>rules. It handled it no problem and didn't drop any packets.
>
>
>
>Now I've upgraded to a big beefy server, gig Ethernet, RH Linux 8.0 and
>Snort 2.0.5 using the same Snort config as above. Traffic levels are
the
>same. Now I noticed it was dropping half of the traffic! My custom
>content rules are extremely important to me, so I performed a test. I
>created this bare bones snort.conf which basically disables all
standard
>rules and extra preprocessors:
>
>
>
>var HOME_NET [10.10.0.0/16]
>
>var EXTERNAL_NET !$HOME_NET
>
>preprocessor frag2
>
>preprocessor http_decode: 80 unicode iis_alt_unicode double_encode
>iis_flip_slash full_whitespace
>
>include classification.config
>
>include reference.config
>
>include /etc/snort/my.rules
>
>include /etc/snort/pass.rules
>
>
>
>Then I started Snort and let it capture traffic for a while. I stopped
>Snort and it is STILL dropping 48% of the traffic! My "my.rules" file
>contains a few hundred content-based rules. What gives? Can Snort no
>longer handle content-based rules? Or am I missing something here?
>
>
>
>Thanks,
>
>Paul
>
>
>
>
>
>
>

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