Snort mailing list archives
Re: snort and network tap
From: Jeff Nathan <jeff () snort org>
Date: Thu, 17 Oct 2002 13:19:49 -0700
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Peter, your finisar, formerly shomiti, network tap will split the transmit pair from either side of a connection into its own port. I've made an attempt to illustrate this here: http://www.snort.org/docs/100Mb_tapping1.pdf Connecting the two tap ports to a hub would hypothetically work in that each Ethernet frame received is broadcast to all ports. Imagining that the tap connected to the hub would use two ports on the hub with a third port connected to an interface on a system running snort, you would see both sides of the connection. In the context of TCP stream reassembly, it's basically essential that you see both sides of a connection otherwise stream reassembly is much less effective and nearly impossiible. One method of using a tap is illustrated in the aforementioned pdf, where the two tap ports are connected to a switch. The two ports on the switch are then set-up to copy all the Ethernet frames they receive to a third port, usually called a SPAN port in Cisco nomenclature. If the SPAN port is also 100Mb, this port can be saturated with traffic as a full-duplex 100Mb Ethernet connection can transmit 100Mb in *each direction*. Alternatively, you could use a Gigabit interface for your SPAN port and hypothetically avoid any port saturation issues: http://www.snort.org/docs/100Mb_tapping2.pdf Another method, described in the archives of this mailing list, involves using interface bonding or bridging. Depending on your Operating System, you can combine two interfaces into a third "virtual" interface which you could then use for snort's packet capture (you would specify this interface using the -i command line switch). Depending on your Operating System and environment, this might work well although this approach has not yet been well tested to my knowledge. Good luck. - -Jeff - --On Wednesday, October 16, 2002 12:06:34 -0500 Peter Erickson <redlamb () redlamb net> wrote:
I am in the process of attaching snort to a network and am not too sure on how to attach it with the network tap that I have. I have the Finisar UTP IL/1. I have been told to connect the 2 tap ports on the Network Tap to a hub and then connect the snort machine to the hub, but after reading some articles on the Snort-Users archive, I heard that I wil lose too many packets due to collisions and that this would not be a good choice. I also read on the snort FAQ that I can not run 1 instance of snort to monitor 2 interfaces, so I guess that is not too good of an options either. I am just wondering what the best way to connect my snort machine to the network using the network tap that I have. Thanks in advance. ------------------------------------------------------- This sf.net email is sponsored by: viaVerio will pay you up to $1,000 for every account that you consolidate with us. http://ad.doubleclick.net/clk;4749864;7604308;v? http://www.viaverio.com/consolidator/osdn.cfm _______________________________________________ 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
- -- http://www.snort.org/~jeff (pgp key available) "Great spirits have always encountered violent opposition from mediocre minds." - - Albert Einstein -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (OpenBSD) iD8DBQE9rxtpEqr8+Gkj0/0RAuyOAJ9xo7nAl7wQNvSBMFphZlJe4M1ZNgCfWnGo 5KPBlEWOA8ufRA8zfKztX2A= =9NF6 -----END PGP SIGNATURE----- ------------------------------------------------------- This sf.net email is sponsored by: viaVerio will pay you up to $1,000 for every account that you consolidate with us. http://ad.doubleclick.net/clk;4749864;7604308;v? http://www.viaverio.com/consolidator/osdn.cfm _______________________________________________ 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 and network tap Peter Erickson (Oct 16)
- Re: snort and network tap Michael Boman (Oct 16)
- Re: snort and network tap Bennett Todd (Oct 16)
- Re: snort and network tap Peter Erickson (Oct 16)
- Re: snort and network tap Scot Scot (Oct 16)
- Re: snort and network tap Jeff Nathan (Oct 17)
- Re: snort and network tap Michael Boman (Oct 16)