Re: Does listening to my network create extra traffic?

From: Dave Korn (no.spam_at_my.mailbox.invalid)
Date: 10/24/03

Date: Fri, 24 Oct 2003 14:54:57 +0100

<> wrote in message
> "Randell D." <> wrote in message
> > well... if I'm listening to my network, am I doing just that?
> Yes.
> > Will these
> > programs create any extra traffic on my network?
> No. Programs that monitor network traffic do not add to the volume.

.... except that a lot of them (tcpdump and ethereal included) will send DNS
requests to convert the IP addresses they see into human-readable names for
their output. Most software of this kind also has options to disable
name-resolution, but at least for the two I mentioned, it's not done by

  It's generally not a great deal of traffic, but just suppose for example a
box on your network gets hit by some slammer style-worm that goes sending
packets to random addresses? Then for every packet the worm sent, your
network sniffer would send a DNS lookup request, and your DNS server would
send a reply - effectively tripling the amount of traffic the worm itself
would have caused. Apart from this scenario, I can't imagine any other case
where a sniffer would contribute any significant amount of traffic.


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