If single physical interface that member of the etherchannel fails, traffic will be redirected to the second physical link and Etherchannel is still Active. Removal of a physical link from an Etherchannel bundle will result in a different bandwidth of the entire bundle and thus in a different link cost of the Port-channel interface. If the Port-channel interface was the root port, the root path cost of the switch will increase. As a result, the spanning tree on that switch or on other switches may select a different root port - this depends on the topology of the network.
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