Once on Cisco Catalyst 6509-E, when I collected an aggregation of three ports, traffic began to go through only two ports and a message appeared in the logs:
%EC-SP-5-CANNOT_BUNDLE_LACP: Gi1/7 is not compatible with aggregators in channel 1 and cannot attach to them (trunk mode of Gi1/7 is dynamic, Gi1/8 is trunk)
All three ports were configured the same:
interface GigabitEthernet1/6 switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 228 switchport mode trunk switchport nonegotiate no cdp enable lacp rate fast channel-protocol lacp channel-group 1 mode active end interface GigabitEthernet1/7 switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 228 switchport mode trunk switchport nonegotiate no cdp enable lacp rate fast channel-protocol lacp channel-group 1 mode active end interface GigabitEthernet1/8 switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 228 switchport mode trunk switchport nonegotiate no cdp enable lacp rate fast channel-protocol lacp channel-group 1 mode active end
I solved the problem by removing the port from the aggregation, repeated the settings and again added the port to the aggregation:
interface GigabitEthernet1/7 shutdown no channel-group 1 mode active switchport mode trunk channel-group 1 mode active no shutdown
After that, traffic began to go through all the ports.
Such an error can also occur due to different port settings, a detailed reason is usually written in brackets, as I have for example “(trunk mode of Gi1 / 7 is dynamic, Gi1 / 8 is trunk)”, although they were configured the same way, perhaps in my case there was a bug.
See also my article:
Configuring link aggregation on the Cisco Catalyst 6500