Re: sniffers





On Feb 24, 2006, at 10:19 PM, Bilal Abdullah Fakhruddin wrote:



Hello,

Recently I am facing problems in my network. Sometimes the network is fast
and sometimes it is slow. Im a bit familiar with Ethereal, but i dont know
what I am looking for. Could anybody help me out by pointing out where i
could start or to any documents available? Thanks in advance.

Regards,

Bilal


You need to start with a baseline or failing that, be prepared to grab packets during a "slow" period. Remember that a sniffer in a switched network is subject to the same limits as any other device, it will only see broadcast packets and packets destined to it. So you need to "mirror" or "monitor" a port or ports or VLAN. The other option is to find a link where traffic funnels to and stick a passive tap or hub in-between the endpoints. I have a network where I keep three different cables patched and ready to go at a moments notice.

Right now I'm testing Lanhound since it will let you have remote sniffers feeding back to the master. It is a design much like Distributed Sniffer from NAI/Network General but it's ALOT cheaper :)

For the initial captures, catch everything, no filters except your own MAC. Always filter out your own MAC address.

For more information, wander by http://www.packet-level.com/ where Laura Chappell has some excellent papers, tutorials and more for folding, spindling and mutilating packets :)

MikeS
hackamac.packetattack.com


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