To make CATIA R21 run as fast on Windows 11 as it did on Windows 7:
Legacy versions require a properly configured License Server or local license file: Create License Folder : Navigate to C:\ProgramData\DassaultSystemes install+catia+v5+r21+on+windows+11+updated
“License server unreachable” – fixed by running DSLS as Admin and disabling IPv6 on the loopback adapter (Control Panel > Network > Adapter settings > Disable IPv6 on localhost). To make CATIA R21 run as fast on