Troubleshooting Etherchannel

Hello Christopher

The port channel load balancing feature that you are referring to is the port-channel load-balance method command. This command sets the load distribution method that will be used to distribute traffic among the ports in the bundle.

The available methods are the following:

* dst-ip—Load distribution on the destination IP address
* dst-mac—Load distribution on the destination MAC address
* dst-port—Load distribution on the destination TCP/UDP port
* src-dst-ip—Load distribution on the source XOR destination IP address
* src-dst-mac—Load distribution on the source XOR destination MAC address
* src-dst-port—Load distribution on the source XOR destination TCP/UDP port
* src-ip—Load distribution on the source IP address
* src-mac—Load distribution on the source MAC address
* src-port—Load distribution on the source port

Essentially each of the above methods makes the specific parameter go over the same link every time. That is, if there is traffic to many different destination IP addresses going over the bundle, packets with the same destination IP address will always use the same link in the bundle. These must be used with caution because if, for example, you use the dst-mac method and all traffic going over the EtherChannel bundle has the same destination MAC, then ALL traffic will go over only one physical link of the bundle, drastically reducing the efficiency of the bundle! This can easily be the case if you have a default router on the other end of the EtherChannel. Make sure you have enough variety of IPs/MAC/Ports on each end to justify your load balancing method.

You can find more information about load-balancing over EtherChannel from Cisco here and more about this specific command at Cisco’s command reference.

I hope this has been helpful!


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