Snort mailing list archives
RE: Snort on switched network
From: "Gadrow, Jim" <jgadrow () cincom com>
Date: Tue, 9 Oct 2001 16:57:54 -0400
Hi Erik, Just a quick comment on your reply to Ashley, please correct me if I'm wrong... The tap used as you suggest will not show you the traffic between hosts on the switch, just the traffic between this switch and other devices. So if I have a 10.1.x.x switch and a 10.2.x.x switch, I can read traffic from 10.1.x.x <-> 10.2.x.x, but not 10.1.x.x <-> 10.1.x.x or 10.2.x.x <-> 10.2.x.x. AFAIK, the only way to watch all of it would be to tap ALL ports, or use a host-based IDS. It actually might work if you tap at least 1 port on each blade of the switches as well. When I use promiscuous mode on a port on a switch, I only see traffic on that particular blade. Not sure how promiscuous mode might work using the tap though... If that's not true or if there's a better way, let me know because I'm in that exact situation. Regards, Jim -----Original Message----- From: Erek Adams [mailto:erek () theadamsfamily net] Sent: Tuesday, October 09, 2001 2:25 PM To: Ashley Thomas Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] Snort on switched network On Tue, 9 Oct 2001, Ashley Thomas wrote:
It is a bad idea to run Snort (or any IDS for that matter) on a switched network, am i right ? Are there any work arounds ?
No, it's not a 'bad thing', you just may not get what you expect. Switches manitain a list of MAC addresses and what port they are connected to on the switch. They only send traffic destined for that MAC down that port. In other words, you usually can't sniff all the traffic. Workarounds? Well, if your switch has a port designed for monitoring, or you can configure spanning (some Ciscos) or port mirroring you'll see all of the traffic. If that's not possible, then drop about $400 on a Shomiti tap. You can place that in front of the switch and get the same results as spanning/mirroring. Hope that helps! ----- Erek Adams Nifty-Type-Guy TheAdamsFamily.Net _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- Snort on switched network Ashley Thomas (Oct 09)
- Re: Snort on switched network Erek Adams (Oct 09)
- Re: Snort on switched network niceshorts (Oct 09)
- Re: Snort on switched network Chuck Morford (Oct 09)
- Re: Snort on switched network Mike Shaw (Oct 09)
- <Possible follow-ups>
- RE: Snort on switched network Gadrow, Jim (Oct 09)
- RE: Snort on switched network Erek Adams (Oct 09)
- Re: Snort on switched network Erek Adams (Oct 09)