Hi @vincentgruber8 ,
i make some test and works for me(all in multilayer switch).
I do this:
Test 1
Switch(config)#int po 1
Switch(config-if)#no switchport
Switch(config-if)#ip add 192.168.0.1 255.255.255.0
Switch(config-if)#ex
Switch(config)#int ra f0/1-2
Switch(config-if-range)#channel-group 1 mo on
By doing this, the system gave me this message:
Command rejected (Port-channel): Either port is L2 and port-channel is L3, or vice-versa
To fix it, run this:
Switch(config-if-range)#no switchport
Switch(config-if-range)#channel-group 1 mo on
Test2
Switch(config)#interface range fastEthernet 0/1-2
Switch(config-if-range)#no switchport
Switch(config-if-range)#channel-group 1 mode on
Switch(config-if-range)#ex
Switch(config)#interface port-channel 1
Switch(config-if)#ip address 192.168.0.1 255.255.255.0
Test3
Switch(config)#int ra f0/3-4
Switch(config-if-range)#channel-group 2 mo on
Switch(config-if-range)#ex
Switch(config)#interface port-channel 2
Switch(config-if)#no switchport
Switch(config-if)#ip add 192.168.2.1 255.255.255.0
Therefore, I recommend making sure you are working on a switch layer 3.
If you keep the problem, you can compress your exercise (winzip) and attach it to check.
Regards