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Broadcom Link Aggregation Team With 2x Cisco 2950

Posted on 2010-11-19
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Hi,

I have setup NIC teaming on a server that has 2x 1Gbps Broadcom NICs in it. I have set the teaming mode to be Link Aggregation (802.3ad)

The switching setup consists of 2x Cisco 2950 NICs, which have been connected together using 2x crossover cables (there has been setup a port channel with switchport mode trunk and channel-protocol lacp for the 2 ports that the x-over cables are plugged into). The switches should be setup so that any one of them could fail, and the network would still function

Each NIC is connected to a different switch

I have not configured any particular options for the ports that the NICs are plugged into (beyond assigning a VLAN, turning off spanning tree, and setting the port speed).

When testing the machine's network throughput, I can see that only 1 NIC is being used - it doesn't seem to be aggregating the connection over both the NICs

I am guessing that there if further configuration that I need to do on the Cisco switch ports that the NICs are plugged into - maybe explicitly enabling LACP?

Whilst I understand how the switches are linked, I actually didn't setup them up myself, so what I'd like to know is the exact config setup that I need to do to the switch ports to achieve our 2 main goals:

1) When both switches are connected and fully functioning, we get an aggregated link - so that we effectively double the network throughput of the machine using both NICs
2) If one of the switches fails, then the network will still function (albeit at a reduced rate as only 1 NIC will be plugged into a functioning switch)

As a picture speaks 1000 words, I have uploaded a simple diagram of the setup as it is.

Regards A simple diagram of the server + switch setup
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Question by:irc-corp
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cstosgale earned 2000 total points
ID: 34176132
Can't do this to two seperate switches I am afraid unless they are stacked (which you can only do with 3750s). Nexus switches can do this but that's another step up in cost.

With your current setup, you can either have active/standby into the switches and have it use only one nic at a time, or you can plug both NICs into the same switch. If you do the latter, you would need to perform this configuration under the switchports to enable LACP (802.3ad) (Make sure the config is the same on both ports first):-

int range fa0/2 - 3
channel-group 1 mode active

Make sure the number you choose for the port channel (1 in the example above) is not already used on the switch using:-

show etherchannel sum

in exec mode.

Once you have enabled the etherchannel you can use the above command to confirm it has negotiated correctly (each port should have a (P) next to it).

Having said all this, do you actually need 2 Gb of bandwidth to the server? Remember it won't actually give you 2 Gb of throughput over 1 connection to the server, but you could have 2 1 Gb connections concurrently.

I have rarely seen this sort of bandwidth actually being used except in bigger enterprise networks. If you are a larger enterprise, you can probably afford a couple of 3750s which you could stack :)
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