RE: Snort IDS + TAPS

[PPowenski () oag com]

am using this method myself and it works well.

-----Original Message-----
From: Chris Reining [mailto:creining () packetfu org] 
Sent: 13 November 2003 16:23
To: Eric Hines
Cc: focus-ids () securityfocus com; snort-users () sourceforge net
Subject: Re: Snort IDS + TAPS


Eric,
I would recommend using channel bonding module under linux to aggregate the
RX and TX streams from your INTERFACE 1 and INTERFACE 2 and run snort on the
bonded interface.

I use it like so to bond eth0 and eth1 together to interface bond0:

/etc/modules.conf:
alias bond0 bonding
options bond0 miimon=100 downdelay=0

/etc/sysconfig/network-scripts/ifcfg-bond0:
DEVICE=bond0
USERCTL=no
ONBOOT=yes

/etc/sysconfig/network-scripts/ifcfg-{eth0,eth1}:
DEVICE=eth0
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes

Note that when a program such as snort or tcpdump sets the bonded interface
in PROMISC mode it will be propagated down to the trunks.

Also see bonding.txt doc.

Hope this helps,
Chris

On Wed, Nov 12, 2003 at 01:23:45PM -0800, Eric Hines wrote:
> All:
>
> We are deploying Snort on a two interface appliance, connected to a 
> GigE
> Netoptics Ethernet TAP. By design, TAPs are split up into (2) monitoring
ports, 
> (RX split up between two ports):
>
> INTERFACE 1 - (from router -> switch) [ ]
> INTERFACE 2 - (from switch -> router) [ ]
>
> Obviously because the RX is split up between 2 ports, if we bind Snort 
> to
> interface 1, it will only see traffic from ROUTER -> SWITCH. If we bind
Snort 
> to inteerface 2, it will only see traffic from SWITCH -> ROUTER.
Therefore, we 
> must bind Snort to both interfaces to see both sides of the session.
Here's 
> where the problem is. If 2 separate Snort processes are monitoring two 
> interfaces, how is the Snort on each interface going to maintain state for
all 
> the connections? Each snort process only sees 1/2 of the connection! 
>
> I've spoken to someone that has said Snort requires modification to 
> listen on a
> tapped device because of this very issue. Someone please advise.
>
>
> -------------------------------------------
> Eric Hines
> CEO, Chairman
> Applied Watch Technologies, Inc.
> web: http://www.appliedwatch.com
> email: eric.hines () appliedwatch com
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see demos from more than 250 industry vendors. If your job touches
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