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Date:      Mon, 14 Oct 2002 19:49:37 -0700
From:      Mike Hogsett <hogsett@csl.sri.com>
To:        Koroush Saraf <koroush.saraf@lmco.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: Monitor IP Traffic from many BSD computers 
Message-ID:  <200210150249.g9F2nb1J019654@axp.csl.sri.com>
In-Reply-To: Message from Koroush Saraf <koroush.saraf@lmco.com>  of "Mon, 14 Oct 2002 18:46:30 PDT." <002d01c273ec$afb22900$6400000a@BSDWIN2KKOROUSH> 

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If you intend to send the captured packets to the console host via the
same interface they were captured from this will multipy the network load
tremendously.  And if you also have the console host do the same this too
will likely cause your network to become overloaded sending the packets
captures.  I don't think this is a practical approuch.

It may be practicle if you place a second NIC in each machine and create a
second network only for sending the captures to the console host.  This
too is likely not the best solution.

I would recommend that you find your self a switch with a more functional
SPAN port, such as an old Cisco 2900.  The Catalyst series SPAN ports are
much more capable.  I often dump all the traffic from any one of a number
of VLANs from the 2900.

But mind you if your network is heavily loaded your SPAN port wont have
the bandwidth to keep up with the traffic.

 - Mike Hogsett

> I have a pool of bsd computers, connected together via an ethernet switch.
> I like to monitor the traffic that is exchanged between all the computers,
> and capture and display them on a console computer.  Since I'm using a
> switch, I will not be able to see the traffic and also the switch is a 3com
> superstack II -3300 which can only monitor one port at a time, so that
> option is out also.  I like to know how I can setup the pool of bsd
> computers, so that they send a copy of whatever packet they receive to the
> console computer so that I can capture and graph it using a utility like
> etherape.
> 
> thanks for your help,
> ~koroush
> 
> 
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