[Snort-users] Quick questions about recieved packets

sekure sekure at ...11827...
Wed Oct 26 07:52:36 EDT 2005


Do you know approximately how much traffic you are trying to monitor?

Definitely make use of the MMAPed pcap library recommended by someone
already, i saw some drastic improvements with it.

Also, enable perfmonitor, tell it to dump stats every minute or so and
let it run for 30 minutes. This will give you a better idea of the
throughput and the CPU utilization.  Post those results back to the
list

When all else fails, you can start disabling rule sets.  Do you really
need every single rule enabled?

On 10/26/05, Joseph Nicholson <wjnicholson at ...11827...> wrote:
> These are onboard NIC's that came with the board I got from Supermicro.
>
>  2 x Intel(r) 82541 Gigabit Ethernet Controllers
>
> I have been thinking about adding a PCI NIC just to see if there is a
> difference.
>
> On 10/26/05, Joshua Berry <JBerry at ...12157...> wrote:
> >
> > What kind of NIC's are you using on the Sensor?  I have had some issues
> with certain cards (mostly Realteks) on Linux, the Intel NIC's seem to work
> the best and you can enable device polling (NAPI) in the kernel for some of
> these cards as well which will boost performance.
> >
> > ________________________________
> From: snort-users-admin at lists.sourceforge.net [mailto:
> snort-users-admin at lists.sourceforge.net] On Behalf Of
> Joseph Nicholson
> > Sent: Wednesday, October 26, 2005 8:25 AM
> > To: snort-users at lists.sourceforge.net
> > Subject: Re: [Snort-users] Quick questions about recieved packets
> >
> >
> >
> >
> > I was afraid of that.
> >
> > I have snort plugged into a Cisco 3560G Switch on a mirrored port.  I am
> mirroring 10 other ports on the switch currently.  This is my core switch
> and brings about 5 different network segments together.  I am using the
> Official Snort Rules and the Bleeding Snort Rules.  Snort is setup to kick
> out the Alerts via Syslog.  The local Syslog function in Linux is setup to
> send the Alerts to a Syslog appliance that parses all of my logs for me.
> >
> > For testing I setup Snort to output Alerts via unified logging and that
> didn't help any.  I currently have both Tx and Rx being mirrored to my
> monitoring port.  I tried just Tx and just Rx and got the same result.  The
> monitor port is a Gigabit port and the monitoring ethernet port is running
> at a Gigabit also.  On the linux appliance that port is running in
> promiscuous mode and has no IP.  I have a management interface on the box
> also that I use to send the syslog files across and that I log into to
> manage the box.
> >
> > Any thoughts or suggestions would be appreciated.  This is the first
> production Sensor I have setup.  All my testing sensors apparently didn't
> have enough traffic being pushed at them.
> >
> >
> > On 10/26/05, Richard Bejtlich <taosecurity at ...11827... > wrote:
> > > Joseph Nicholson wrote:
> > >
> > > >I see that snort dropped 179457 packets because it couldn't process
> them.
> > > > Snort received 186246 packets
> > > > Analyzed: 6789(3.645%)
> > > > Dropped: 179457(96.355%)
> > > > My gut instinct is telling me that it dropped 179457 packets because
> it
> > > > felt there was no threat from them and that the 6789 it analyzed
> looked
> > > > suspicious.
> > >
> > > Hi Joseph,
> > >
> > > You have a serious problem with your Snort deployment.  The packets
> > > Snort dropped were never inspected, period.
> > >
> > > Can you describe your configuration?  Are you sending Snort alerts
> > > directly to a database, without Barnyard?  Are you running any odd
> > > rules?
> > >
> > > Sincerely,
> > >
> > > Richard
> > > http://www.taosecurity.com
> > >
> >
> >
> >
> > --
> > Joseph Nicholson
>
>
>
> --
> Joseph Nicholson




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