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In a basic network you have two ethernet ports that go to two separate switches. These switches are on the same subnet

If I take a basic consumer grade switch (nothing fancy) and hook it up to both switches, will it load balance (as in take two 100mb links and theoretically make it one 200mb link) between the two switches or will it just use one and turn the other one off?

IE is this kind of load balancing common in consumer grade switches?

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What do you mean by "on the same general network"? Can you be a bit more specific? – mdpc Sep 27 '11 at 17:28
By consumer-grade I assume you mean "piece of junk unmanaged device" ( or similar)? – voretaq7 Sep 27 '11 at 17:32
No, without something like spanning tree, you're going to end up with a loop and ensuing broadcast storm that will incapacitate your switches. – EEAA Sep 27 '11 at 17:32
@mdpc They are in the same subnet – TheLQ Sep 27 '11 at 17:38
I don't follow the question. How could any switch load balance under those conditions? Each of the two links go to different switches, so it has no choice of what goes on what link. If it doesn't know which switch the traffic goes to, it has to put it on both links. If it knows which switch the traffic goes to, it has to put it on the link to that switch. What choice does it have? – David Schwartz Sep 27 '11 at 22:58
up vote 10 down vote accepted

Not quite. What you're looking for is link aggregation. What you're likely to do by doing this is to create a switch loop, which would be a bad thing.

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You'll only create an Ethernet loop if both interfaces have the same MAC. So pretty much only if the two NICs are bonded on the server. – MDMarra Sep 27 '11 at 17:31
Depends on how smart the upstream switches are - If they do STP they'll negotiate to kill one of the ports because of the loop. If they don't your network will collapse. Civilization will follow. When your netadmin finds the device responsible for the loop you may lose the ability to procreate... – voretaq7 Sep 27 '11 at 17:34
Or TRILL! One of these days... – Shane Madden Sep 27 '11 at 17:38
Thanks for actually explaining it, I was afraid that it would create a loop – TheLQ Sep 28 '11 at 1:06


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You'll probably just end up with a loop (...if spanning tree isn't running on the switches - which 99% wont).

There are indeed consumer grade switches, with uplink ports setup so that they can be bundled (ie 2 cables from switch to switch = 2Gbps connection) but that's just between those specific ports and between identical switches.

For example I'm using the HP Procurve 1810G-24 switch which has two ports (23 & 24 - see image here ) which can be used in combination to create a 2Gbps link between two same HP switches.

On a Cisco switch you can configure ports to be part of an EtherChannel Link in order to increase bandwidth between two switches. link

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