Etherchannel

Unanswered Question
Jan 15th, 2009
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my question is regrading bandwidth

i have a lab setup going to test end to end client speed.

each client is connected to a gig-E interface.

with a etherchannel running on two FastEthernet ports.


the question is can the two clients achieve throughput of more than 100Mbits with this kind of setup?


i have not been able to test this setup do to lack of equipment but i am try to straighten out if the load balancing that etherchannel preforms will cap you to 100mbits on a single point to point connection.

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glen.grant Thu, 01/15/2009 - 05:28
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No any given conversation between devices will flow down a single pipe in that etherchannel group so getting over 100 meg i snot possible in a fastethernet port channel. Total traffic is divided between the ports in the channel group depending on how the channel is setup whether it be source destination address or source destination mac address .

Joseph W. Doherty Thu, 01/15/2009 - 06:55
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Etherchannel may "hash" different flows across its channels. (Hash criteria can sometimes be configured, often based on some combination of L2 or L3 addresses.) This would allow up to the combined bandwidth of all channels, however a single flow will only use one channel; multiple flows might map to the same channel.


So, two clients might hash to one channel link each, providing 200 Mbps, or they might hash to the same channel, where they will share 100 Mbps (while the other link remains idle). Channel hashing is deterministic and static (i.e. not sensitive to any actual link load). I.e., given the same flow parameters, traffic will be directed to the same channel.


PS:

Default channel hashes will often direct all traffic to the same channel. Examples would include source L2 MAC from a gateway or destination L2 MAC to a gateway.


[edit]

PPS:

Tshi's reference link has additional details.

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