EtherChannel - Maximum Number of Physical Links
On Cisco devices, the maximum number of ports in an EtherChannel is primarily determined by the switch platform and its hardware/firmware capabilities, and not directly by the EtherChannel protocols themselves, such as PAgP, LACP, or manual EtherChannel configurations. However, the protocols do have some influence in how those ports are managed.
On most platforms, the maximum number of ports an EtherChannel can support, regardless of how you configure it, is generally the same. For most Cisco devices, each EtherChannel can support up to 8 active ports.
When using either LACP or PAgP it is possible to configure more than 8 ports, typically up to 16. In such a case, by default, eight will be active, and eight will be in standby mode. This means that if any of the active ports fail, one or more of the standby ports will transition to active, ensuring that there are still eight active ports in the EtherChannel.
When using LACP you can configure the max-bundle value to change the number of active links you want in your EtherChannel, and you can also adjust the LACP port priority to determine which ports become active in such a case.
When using PAgP, you can configure parameters such as port priority to control which ports will become active.
Manual EtherChannel configuration cannot take advantage of standby ports.
Links:
https://forum.networklessons.com/t/troubleshooting-etherchannel/1186/30?u=lagapidis
https://networklessons.com/switching/troubleshooting-etherchannel/