network monitoring..

Here is a senario, would I still be able to effectively monitor the network traffic?

I have two managed HP switches stacked together with most of the clients and servers on it, I have another unmanaged HP switch with some clients on it, that unmanaged switch is connected to the managed stack with a cat5 cable. I would imagine this would work fine since the traffic from the unmanaged switch would flow through the managed stack, and into the monitor port that the sniffer is connected to.

Thanks in advance!
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The monitor port is set to span other specific ports. If the unmanged switch connects to port 2 and you have port 1 set to monitor port 2 then you will see any traffic coming across port 2 to your switch on port 1. If the two systems that are talking to each other, however, are on the same unmanged switch, you will never see the traffic.

In the below example, if you have the correct port monitored on switch two, you will see traffic from PC1 and PC2 going to PC3 but you would not see traffic from PC1 going to PC2.

PC 1          PC 2                             PC3
|               |                                  |
SWITCH ONE ------------------SWITCH TWO

cbtechAuthor Commented:
So in my case, since I have the two managed switches stacked, making them virtually one, any traffic between the two managed stacked switches and the unmanaged one I could see, but any traffic local to the unmanaged switch I cannot see, since it doesnt come across from the unmaged switch to the managed stack?

syn_ack_fin is correct.

You won't see any traffic that stays on the unmanaged switched and never comes over into the manages switches.
We use Paessler Router Traffic grapher -

You can set it up to monitor any port on the managed switches if you enable SNMP.  Gives you nice graphs of traffic going in and out of any port in real time.  But like the other guys said, any traffic staying within the unmanaged switch can't be monitored.

Try out the program - the free edition allows you to setup one monitor - so you can try monitoring one port and get an idea of the traffice.  The full version is pretty cheap - $49 I think.  Runs a service on any windows computer.  I highly recommend it.
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