SPAN is fine unless you do something silly. I use RSPAN and ERSPAN all the time 
for troubleshooting, often mirroring more than 300 Mbs / 40Kpps - no worries.

________________________________

From: [email protected] 
To: [email protected] 
Sent: Fri Jan 30 07:57:25 2009
Subject: Re: [Ntop] Non IP Traffic 


That's all he will see unless he gets the NetFlow plugin operating on a switch 
or router in his network.  Or, he could have his PC connected to a SPAN port 
(not recommended, could clog the switch).  3kb/s of traffic is not going to 
kill his WS.  Pretty typical.  I have a site I'm working on currently with 
30kB/s of broadcast noise.  Not much in 100 mb/s links.


On Thu, Jan 29, 2009 at 10:49 PM, Burton Strauss III <[email protected]> 
wrote:


        Well, what you are seeing is a varied collection of broadcast traffic...
        
        ARP - address resolution protocol - is how you find an address on the 
LOCAL
        segment.
        
        NBNS - NetBIOS, a local (non-routable) protocol
        
        MS NLB - Microsoft Network Load Balancing protocol
        
        Etc.
        

        -----Burton
        
        -----Original Message-----
        From: [email protected] [mailto:[email protected]] On Behalf Of
        Martin Larsson
        
        Sent: Thursday, January 29, 2009 6:47 AM
        To: [email protected]
        
        Subject: Re: [Ntop] Non IP Traffic
        
        Everything is just running on my local machine, yes.
        All I'm trying to do is to understand why my network-adapter is 
receiving
        all that data. It looks like there's a fairly constant stream of about
        3Kbits...
        
        But thanks for the info, I'll do some more simple checks and notify my
        admins.
        
        M.
        
        On Thu, Jan 29, 2009 at 3:27 PM, Walt Henley <[email protected]> 
wrote:
        > This trace may not be telling you the whole story.  Did you put the
        > Wireshark machine on a SPAN port or just run it locally connected at 
your
        > PC?  If you ran it locally connected, then all you are seeing is your
        > traffic and any broadcasts that come along.  Also, how are you 
collecting
        > NTOP data?   Using NetFlow or Sflow or just with a local connection.
        Could
        > be that it is seeing the heartbeats and deciding they are not 
identifyable
        > IP traffic.  Try running netflow on your ethernet switches (assuming 
they
        > are Cisco)>
        >
        > On Thu, Jan 29, 2009 at 8:59 AM, Martin Larsson 
<[email protected]>
        > wrote:
        >>
        >> Thanks. WireShark was interesting, and overwhelming.
        >> It seems there's a lot of "MS NLB Heartbeat" each containing 1510 
bytes.
        >> Could that be it?
        >> I've attached a sample screenshot.
        >>
        >> On Thu, Jan 29, 2009 at 2:16 PM, Burton Strauss III
        >> <[email protected]> wrote:
        >> > It means ntop is seeing a lot of traffic that isn't recognizable as
        >> > tcp/ip.
        >> >
        >> > Depending on your connection and what you are monitoring (network
        >> > topology)
        >> > this could be normal (i.e. traffic wrapped in something) or it 
could be
        >> > odd.
        >> >
        >> > I usually recommend installing WireShark and letting it analyze a 
few
        >> > dozen
        >> > packets (they both use libpcap so they look at traffic the same 
way).
        >> >  If
        >> > WireShark calls it differently than ntop, you probably have exposed
        some
        >> > bug. If they both call it non-ip, then explain your topology and 
we can
        >> > guide you.  If you aren't sure, grab & post a screen shot of a 
page of
        >> > random traffic from WireShark, post it and we can read what you 
have
        >> > from
        >> > there...
        >> >
        >> > -----Burton
        >> >
        >> >
        >> >
        >> >
        >> >
        >> > -----Original Message-----
        >> > From: [email protected] [mailto:[email protected]] On 
Behalf Of
        >> > Martin Larsson
        >> > Sent: Thursday, January 29, 2009 3:54 AM
        >> > To: [email protected]
        >> > Subject: [Ntop] Non IP Traffic
        >> >
        >> > I installed ntop because the system monitor told me my network was
        >> > fairly
        >> > active
        >> > even though I wasn't actively sending or receiving anything.
        >> > After about 1.5 hours of running, the traffic summary is showing 
me a
        >> > lot of
        >> > non-IP traffic.
        >> >
        >> > Total   26.4 MBytes [47,672 Pkts]
        >> > IP Traffic      9.3 MBytes [26,718 Pkts]
        >> > Fragmented IP Traffic   0 [0.0%]
        >> > Non IP Traffic  17.1 MBytes
        >> >
        >> > What does that mean?
        >> >
        >> > M.
        >> > _______________________________________________
        >> > Ntop mailing list
        >> > [email protected]
        >> > http://listgateway.unipi.it/mailman/listinfo/ntop
        >> >
        >> > _______________________________________________
        >> > Ntop mailing list
        >> > [email protected]
        >> > http://listgateway.unipi.it/mailman/listinfo/ntop
        >> >
        >>
        >> _______________________________________________
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        >
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