Snort mailing list archives

RE: dual nic, was: flex response and cisco span por ts


From: "Burleson, Lee (IA)" <Lee.Burleson () ia ngb army mil>
Date: Wed, 2 Jan 2002 17:45:02 -0600

Byron -

Try unbinding TCP/IP from the non-admin interface(s).  You will need the
latest version of WinPCap to do this.  I have this running successfully in
my environment on several sensors now.

Big smiles to those guys in Italy for that improvement.

HTH.

- Lee

-----Original Message-----
From: Byron [mailto:snail945 () yahoo com]
Sent: Wednesday, January 02, 2002 14:13
To: John Roberds
Cc: snort-users () lists sourceforge net; tyler () ibill com
Subject: Re: [Snort-users] dual nic, was: flex response and cisco span
ports


all-

I'm using a dial nic setup as mentioned a few times in this 
thread.  I also
have had issues where packets tried to leave off of the snort 
interface when
i only want them to be routed out the administrative nic on a 
separate vlan
as defined by the cisco 6509.  Usually this only happened if the admin
interfaces went down for some reason.

On windows 2000, how can i allow snort to listen on one nic 
and not have an
ip assigned to this nic?  I'd like to avoid having a second 
default gateway
in the local routing table.  I only want a default gateway 
route for the
administrative LAN.

thx!
----- Original Message -----
From: "John Roberds" <roberdsj () wishard edu>
Cc: <snort-users () lists sourceforge net>; <tyler () ibill com>
Sent: Wednesday, January 02, 2002 10:42 AM
Subject: Re: [Snort-users] flex response and cisco span ports



tf,

The Cisco switches Steve mentions here are both IOS based
switches that by default permit the type of rx/tx on the 
administrative
port by default.  My guess is that you may be using a CLI 
("set") based
switch like the 4K,5K,& 6K family.  I would try the 
additional parameters
inpkts enable on the span setup.  e.g.

6506(enable)# set span 4/40 4/41 both inpkts enable

This should do what you want for the single interface 
solution.  However,
I like the two interface concept to facilitate an 
independent enterprise
wide vlan to collect data.

Good luck,

JR

Graeme Fowler wrote:

tf wrote:

When snort has to respond [ie, send RST packets] I assume it
sends them out the interface it is listening on?
How does this work when monitoring a cisco switched network?
Once I make a port a monitor port, it is read-only and nothing
can be sent out on it, so what I've done in the past is put 2
interfaces on my snort sensors.  One is a listener, the other
is the "management" port that I ssh to, etc, etc.

In my experience, this is wrong on both counts. I have 
successfully used
real live machines (both by accident *and* by design; 
long story) with
real
live IP addresses plugged into a Cisco SPAN (port mirror, 
monitoring,
call
it what you will) port on Catalyst 2924XL and 3524/3548XL 
switches. It
can
make emergency oh-my-god-everything-broke situations a little more
bearable
if you can sniff *and* make external connections thru the 
same NIC,
especially when you have a laptop with a single 
interface... and you
need to
just dig that MAC address out of that remote database 
which is not on
your
laptop!

So I guess my question is this.. Can I make the sensor send it's
flex-response packets out the 'mgmt' port instead?  Surely
there are other people with an environment like this [snort,
cisco catalyst switches, flex-response] .. What's everyone else
doing?

As far as I'm aware, snort chucks its' flexresp packets 
out via *the
default
gateway* therefore it spits them out thru whatever interface your
default
route points at.

YMMV obviously, but as far back as the initial implementations of
flexresp
snort didn't do anything too fancy, just generated the packets and
dropped
them on the IP stack for the kernel to handle as it 
pleased. I'm not too
proud to stand corrected, mind you!

Graeme
--
Graeme Fowler
System Administrator
Host Europe Group PLC

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