It seems this topic has been covered plenty already, but I just thought I would share my experience getting tacacs+ authentication working with enable mode(privilege level 15) for our ASA5550. Probalby unique to my setup, but perhaps this can help anyone else who comes across this problem
In the tacacs.conf file on your tacacs+ server make sure you create a user called $enab15$. This is in addition to your individual user accounts. This is a global "enable" user that is used to authenticate escalating to enable privilege mode for any user in tacacs.conf.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...