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RE: Caching a sniffer
From: "Shawn Jackson" <sjackson () horizonusa com>
Date: Tue, 23 Mar 2004 10:20:48 -0800

If you have a decent network switch in your environment
you can disable all it's port to allow promiscuous mode across the 

From this text I got Port Mirroring, (SPAN). Now you can use MacOff 
(or another MAC flooder) to overload the MAC table in a switch and turn 
on promiscuous mode which will allow you to sniff the network.

I'm aware of SPAN, of course.  I use it routinely to *enable* sniffing,

not PREVENT it.  (I took "Caching" to be an obvious misspelling of 
"Catching" -- was that my mistake?)

No clue, I just caught the last part of this thread, detailed above. But
you're right, SPAN/Port Mirroring allows you to selective monitor a
traffic by forwarding a real-time copy of that traffic to a monitor

What I don't see is how it can be described as "disable all it's 
port to allow promiscuous mode across the network", which sounds 
like maybe it means a switch command to either prevent client 
devices from going into promiscuous mode, or shut down the switch 
ports of clients who do.  If such a command existed, it would be 
a great way to prevent users from sniffing each other's traffic, 
but I don't believe it does.

In essence if you flood the MAC table of a switch the switch will turn
into a hub, thus "disabling the switch component of the ports". You
argue that turning on SPAN/Port Mirroring is also disabling the 'switch'
of that concerned port. 

To my knowledge, though not very extensive, I know of no command/system 
in switches to detect a NIC/Adapter in promiscuous mode and disable the

Shawn Jackson
Systems Administrator
Horizon USA
1190 Trademark Dr #107
Reno NV 89521

Email: sjackson () horizonusa com
Phone: (775) 858-2338
       (800) 325-1199 x338

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