In my setup, WLC (2504) - Switch (WS-C3850-12S) are connected to each other in the production environment. LAG is enabled on WLC end and ether-channel is created on switch end and two interfaces (Gi1/0/1 & Gi2/0/1) are part of ether channel bundle.
Now I am planning to add additional interface in the ether channel bundle. I am observing following error while adding third interface.
XXX(config-if)#channel-group 9 mode on
Command rejected: conflicts with Switch Backup Interface
Please note that I haven't taken any downtime window while making this change hence I cant reboot WLC.
I know that its basic requirement to reboot WLC in order to support LAG if its not previously enabled. I was wondering if WLC reboot is required since LAG has already enabled but not sure as it is not making sense :)
Anyone has experienced this issue ? Appreciate if any one can help with the solution.
The reboot is only required initially when you enable LAG. After that, there should not be any need to reboot again as the LAG has already been enabled. Is the error on the 3850 side or WLC?
Could you share the configuration of this interface?
By the way, try it under interface: no swtichport backup interface
check this link for more information: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/layer2/configuration_guide/b_lay2_3se_3850_cg/b_lay2_3se_3850_cg_chapter_0110.html