Snort mailing list archives

Re: SPAN


From: Alexander Hoogerhuis <alexh () ihatent com>
Date: 30 Aug 2002 22:47:42 +0200

I know I'm late off the block in answering, but if im not wrong you
can span a vlan on the 29x0- and 25x0-switches, but it aint horribly
fast. If your network is a bit sanely designed, there is hope you
might have a central 35x0-switch with the central servers hanging off
it, and trunks out to workgroup-switches (29x0'es). In this setting,
you can easily use a trunk-port and split out the vlans you need on
a linux box, and use snort on the indivudual interfaces you need to
monitor.

If you're a small to medium sized shop you'll be happy with a 100mbit
trunk and if you're in a bigger place you can live off one of the
gbit-uplinks on the 35x0. If you can't feed what you need through the
gbit link you shouldn't be running on a 35x0 anyway :)

mvh,
A

HenkP () masana co za writes:

It all depends on your setup, we have a hub outside the firewall - between
the firewall and our ISP's router, with a snort sensor plugged into the
hub.
Internally we have switches and we use SPAN to one port were another snort
sensor is plugged in for mainly monitoring inside traffic to our servers.
Everything works 100%

Because we are using 2950 catalysts and we dont have a big core switch, I
can only use SPAN on one switch, but this is the switch were all our
servers are connected to, so any traffic destined for them will be caught
on the SPAN port.
If you have a big Catalyst like a 4000, or 5000 or 6000 series core switch
then you can use SPAN not only on a port basis but you can also SPAN vlan
traffic to one port. i.e. SPAN across all internal traffic you have.

hope that gives you some idea,

Cisco's website has plenty information on SPAN
http://www-search.cisco.com/pcgi-bin/search/public.pl?q=SPAN+port&sa=Go&num=10&searchselector=0

Regards

Henk Pretorius




                                                                                                           
                    Chris Keladis                                                                          
                    <Chris.Keladis () cmc optus net.       To:     "Tim" <twr () bellsouth net>, "Snort-list"    
                    au>                                  <snort-users () lists sourceforge net>               
                    Sent by:                            cc:                                                
                    snort-users-admin@lists.sourc       Subject:     Re: [Snort-users] SPAN                
                    eforge.net                                                                             
                                                                                                           
                                                                                                           
                    2002/08/20 03:07 AM                                                                    
                                                                                                           
                                                                                                           




At 05:34 PM 19/08/2002 -0700, Tim wrote:

Quick question, will snort sensors play with monitored ports on a Cisco
10/100 switch or is placing a hub be the better way to setup the sensors?

I'm no switching expert by any stretch of the imagination, but i guess it
would depend on the amount of traffic your looking at.

A monitored port on a switch would work fine for low-traffic environments,
but for higher speed monitoring it's more natural to use a hub.

Personally i like Ethernet taps the best, as they 'tap' into your network
stream and split your traffic to your IDS systems.

One drawback with the taps is that they are usually Read-Only (there may be

RW taps out there, i just have not seen them, myself), so you cant use any
active-response features, which i don't agree with in principal anyway.

Anyway, just my 2quid. :)



Regards,

Chris.



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-- 
Alexander Hoogerhuis                               | alexh () ihatent com
CCNP - CCDP - MCNE - CCSE                          | +47 908 21 485
"You have zero privacy anyway. Get over it."  --Scott McNealy


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