[lug] OT Netwerking Layers 101
Zan Lynx
zlynx at acm.org
Tue Feb 18 16:11:06 MST 2003
On Tue, 2003-02-18 at 15:21, Warren Sanders wrote:
> I'm testing out NTOP; a network traffic probe that shows the network usage
> (ntop.org) on our lan.
>
> Our main panel is an HP ProCurve switch 4000M and is configured to allow my
> connection to monitor the network.
>
> Was connected with a 5 port Linksys switch and found I was getting info from
> only what was going through this switch. I then replaced it with an old 4
> port 10 base Netgear hub and I could then see all the network traffic.
>
> Now I replaced the 5 port Linksys switch with a 5 port Linksys 100 base hub
> (EFAH05W) and I'm back to only seeing my branch of the network. Just for
> kicks I linked off this with another Linksys 10 base hub and moved only my
> connection to this and can see all the network again!
>
> So I'm wondering if the Linksys 100 hub is doing something to the network
> layers that you normally see in a switch (private lines)? I'm confused! I
> don't want to have to us a 10 base hub whenever I need to monitor; why can't
> the 100's do it?
If the Linksys 100 hub is dual speed, then it might have a switch. Dual
speed hubs that can accept 10 and 100 mbit connections at the same time
have a hidden switch that handles moving packets from the 10mbit to the
100mbit, and vice versa.
If you need high efficiency, don't put a hub on your monitoring port at
all. Use a direct connection to your monitoring equipment. A hub will
introduce collisions and you lose full duplex support.
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