Hi,
It is completely possible, You can disable the aggressive mode from the ASA and it will not affect the AnyConnect beacuse it uses (TLS and DTLS protocols)which is completely different from the IPSec.
Now you can disable the aggressive mode as follow:
hostname(config)# crypto ikev1 am-disable
If you have VPN clients IPSec, they will work with main mode if you use certificate authentication only, not using pre-shared keys.
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David Castro,
Regards,