Dell Configuration Guide for the S4048–ON System 9.14.2.5

The common speed is determined when the port channel is first enabled. Then, 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, Dell EMC Networking OS disables them.

Port channels can contain a mix of 1G/10G/40G. The interface speed that the port channel uses is determined by the first port channel member that is physically up. Dell EMC Networking OS disables the interfaces that do not match the interface speed that the first channel member sets. That first interface may be either the interface that is physically brought up first or was physically operating when interfaces were added to the port channel. For example, if the first operational interface in the port channel is a Tengigabit Ethernet interface, all interfaces at 10000 Mbps are kept up, and all other interfaces that are not set to 10G speed or auto negotiate are disabled.

Dell EMC Networking OS brings up the interfaces that are set to auto negotiate so that their speed is identical to the speed of the first channel member in the port channel.