[Snort-users] Snort on home DSL connection

Bell, Josh josh.bell at ...10824...
Sun Dec 28 15:09:00 EST 2003

The problem there is Snort is listening outside my firewall - and since I'm using NAT, that interface will never see a packet to/from 192.168.x.x.  It'll only see packets to/from the dynamic IP my ISP gave me.

	-----Original Message----- 
	From: Erek Adams [mailto:erek at ...950...] 
	Sent: Thu 12/25/2003 6:33 AM 
	To: Bell, Josh 
	Cc: snort-users at lists.sourceforge.net 
	Subject: Re: [Snort-users] Snort on home DSL connection

	On Wed, 24 Dec 2003, Bell, Josh wrote:
	> Another Snort newb here...
	> I've set up a Snort box at home so I can have an 'expendable' box to
	> experiment and learn on.  I have an SBC DSL connection.  The DSL line
	> runs into my DSL modem, from there to a little hub, and from there to a
	> Linksys-type router/firewall, where my machines are connected.  It's a
	> PPPoE DSL connection so my IP can and does change rather frequently.
	> On my Snort box, eth0 is connected to the 'inside' network with an
	> RFC1918 address and eth1 is connected to the hub in promiscuous mode.
	> It receives all traffic that hits the hub, the only problem I have is I
	> don't know how to set the HOME_NET variable.  I can't use eth0's IP
	> because that's just a 192.168 address.  Eth1 has no IP and I don't want
	> to statically plug in in there.  Can I use a DNS name?  I have a DYNDNS
	> account which in theory is updated regularly and should be the IP of my
	> router.  If not, is there some way of telling it to use whatever IP is
	> currently assigned to a particular MAC?
	Use the 192.158.x.x address as HOME_NET.  After all you're looking to see
	what is coming from the internet (var EXTERNAL_NET !$HOME_NET) that's
	coming at you (PPPoE).  Since Snort doesn't handle PPPoE that well, you're
	better off to listen to the 'inside' interface (192.168.x.x) and see
	what's passing "thru" the router/gateway.
	Erek Adams
	   "When things get weird, the weird turn pro."   H.S. Thompson
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