Port LTM and GTM configuration from v10 to v11

What are you upgrading from and to? You may have differences such as interface names, so you could always do this manually or merge a new bigip_base.conf file. The bigip.conf file contains config which is appliance independent so you could always copy a version of this over from the old appliance to the tmp folder and run the following:

tmsh load sys config file /var/tmp/bigip.conf-from-old-appliance merge verify

the 'verify' syntax doesn't load the config, just makes sure it's valid. Once you're happy you can omit that part of the command to load the new config