Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

The common speed is determined when the port channel is first enabled. At that time, the software checks the first interface listed in the port channel configuration. If you enabled that interface, its speed configuration becomes the common speed of the port channel. If the other interfaces configured in that port channel are configured with a different speed, the system disables them.

For example, if four interfaces (TenGig 0/0, 0/1, 0/2, and 0/3) in which TenGig 0/0 and TenGig 0/3 are set to speed 100 Mb/s and the others are set to 10000 Mb/s, with all interfaces enabled, and you add them to a port channel by entering channel-member tengigabitethernet 0/0-3 while in port channel interface mode, and the system determines if the first interface specified (TenGig 0/0) is up. After it is up, the common speed of the port channel is 100 Mb/s. The system disables those interfaces configured with speed 1000 Mb/s or whose speed is 1000 Mb/s as a result of auto-negotiation.

In this example, you can change the common speed of the port channel by changing its configuration so the first enabled interface referenced in the configuration is a 1000 Mb/s speed interface. You can also change the common speed of the port channel here by setting the speed of the TenGig 0/0 interface to 1000 Mb/s.