Greetings!
The caution you pointed out is intended to point out that, if the trunk has not been properly configured on both ends of the connection on all applicable links, a loop may result if all of the trunk ports are enabled.
My recommendation to create a trunk on an Aruba switch on existing ports, per the scenario you described, would be the following:
- Disable the ports you wish to use for your trunk;
- Create the trunk, including the ports you disabled in step 1;
- From the interface context for the new trunk, tag/untag the desired VLANs;
- Ensure that the trunk is properly configured on the device(s) on the other ends of the links;
- Enable the trunk ports.
Here are example commands on the Aruba switch, based on the information you provided:
ArubaSwitch(config)# interface 47,48 disable
ArubaSwitch(config)# trunk 47,48 trk1 lacp
ArubaSwitch(config)# interface trk1 tagged vlan <list of VLANs>
ArubaSwitch(config)# interface 47,48 enable
Note that the port configurations are automatically cleared when they are added to the trunk, so there is no need to do so manually.
Let me know if this is what you were looking for.