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You are here: MacNN Forums > Enthusiast Zone > Networking > upgrading to Gigabit switch, daisychaining, bandwidth

upgrading to Gigabit switch, daisychaining, bandwidth
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Mac Elite
Join Date: Jun 2006
Location: Pittsburgh
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Aug 24, 2012, 07:18 AM
I have 6 4-port PoE switches that are daisychained, the last switch being connected to a 16port 10/100Mbps switch. the data from the 24 PoE devices is being sent to a machine and it's nearly maxing out the 10/100Mbps connection on that machine. If I were to upgrade the 16port switch to Gigabit, could I leave the PoE switches in a daisychain, thus only using one port on the Gigabit switch, or would I have to connected each PoE switch to the Gigabit switch, thus taking up 6 ports? The end result being that ~10% of the NIC being used as opposed to the current ~90%
Posting Junkie
Join Date: Mar 2004
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Aug 24, 2012, 11:44 AM
Is there any particular reason you need to daisy chain 6 switches? Seems like a lot. Cat5e or Cat6 cable is cheap you know.

If you can daisy chain 6, I don't see why you couldn't daisy chain a seventh.
I have plenty of more important things to do, if only I could bring myself to do them....
abbaZaba  (op)
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Aug 24, 2012, 12:12 PM
the point is to get the NIC on the machine pulling in the data up to Gigabit. Currently, it's maxing out the 10/100Mbps; the switch connecting the PoE devices and the machine is only 10/100Mbps. My reasoning was if I upgrade the connection between the two to Gigabit, I'd drop the network utilization down to ~10% and I was unsure if having them daisychained into the Gigabit switch would be a bottleneck: one Cat5e into the Gigabit switch carrying the data from the 24 PoE devices as opposed to the 6 PoE switches carrying 4 devices into the Gigabit switch.

I'm *guessing* it'd be better to have them connected separately, but I figured I'd asked in case anyone else could confirm
Posting Junkie
Join Date: Oct 2005
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Aug 24, 2012, 03:37 PM
If you don't connect each PoE switch to your core switch, your bandwidth between the comptuer and PoE devices is limited to the 100Mbps connection between the last switch and your core switch. It doesn't matter if you have gigabit between your computer and the core switch if the PoE switches are bottlenecked at 100Mbps total.

If, on the other hand, you're just trying to free up some bandwidth for other purposes (connecting to other machines on the 16 port switch, etc), then you can just upgrade the core switch to gigabit and leave all the PoE switches daisy chained.

If you're limited on cabling you could have two daisy chains of 3 switches each, or three daisy chains of 2 switches each, to improve your aggregate bandwidth (and of course a gigabit core switch) to the PoE devices.

FWIW, I assume your PoE switches are actually 8 port switches with 4 of the ports supporting PoE (a common configuration) otherwise you wouldn't have 24 ports available for downstream devices currently. I forget why I thought this mattered.
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