Etherchannel question

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lamav Mon, 03/03/2008 - 14:45
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Etherchannel is used to bundle multiple physical inter-switch ethernet links together so that the switches see them as only ONE logical link, instead of 3, 4 or 5 (up to 8) separate physical links. This will allow you to use the bandwidth of those redundant links without having them blocked by STP.


Switch A and switch B are connected to each other via one dot1q trunk. If you add another dot1q trunk, STP will block that trunk from forwarding user-traffic because it does not allow redundant links that carry the same vlan traffic to exist. It may cause a loop. If you configure ehterchannel on both switches, however, the switches' STP process will not block any additional trunks because they will all be placed in one etherchannel channel group and be seen as only one link.


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Jon Marshall Mon, 03/03/2008 - 14:49
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Generally speaking a single data transfer in one direction will only use one of the available links as etherchannel load balances flows across it's links. What it load balances on can be src/dst mac address, src/dst IP address and port numbers but not all switches support all types of load balancing.




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