You need to read about how a switch works. In short, the switch monitors the network it sees and knows which mac address(es) are on which ports. When it received a packet, it forwards it to only that port. Broadcasts are forwarded to all ports.
So an ntop instance, sniffer, whatever only sees a fraction of the traffic. In many managed switches, there is an option for a "repeater" or "monitoring" or "spanned" port, which receives all traffic, so that network monitoring can be performed there. With multiple switches is a hierarchy, you will have to place the ntop instance or instances carefully, depending upon what you want to monitor. For example, most lans would have a switch in each area with it's uplink connected to a backbone switch. Servers and gateways are then placed off one or more ports of the backbone too. This keeps departmental traffic isolated from each other, while making enterprise wide and inter-department traffic feasible. ntop would have to be monitoring the backbone switch, but you would need to be aware of what ntop is NOT seeing. You could then place additional ntop instances in the departments, using the netflowPlugin program to receive flow information from them which wouldn't be visible to the backbone instance. (I'll note that I haven't actually tried this, myself.) -----Burton -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Laurent DIDIER Sent: Saturday, April 27, 2002 3:02 AM To: [EMAIL PROTECTED] Subject: [Ntop] help for understanf the ntop Good morning, Sorry for my bad english, but. I write because i d'ont understand how ntop make for pass my switch, i have install NTOP on a linux box, and i see all computer on my network, but i have 9 switch on this network. above the switch block the passage of all information, because the switch work on mac adress. Thank for your comment Rien de grand ne c'est accompli dans le monde sans passion --------------------------------------------- Alfred ENGEL FORLAN http://www.forlan.com _______________________________________________ Ntop mailing list [EMAIL PROTECTED] http://listgateway.unipi.it/mailman/listinfo/ntop _______________________________________________ Ntop mailing list [EMAIL PROTECTED] http://listgateway.unipi.it/mailman/listinfo/ntop
