Hi!
your problem with the no global sessions-Numbes I couldn´t help (but I you have a solution please let me know!)
RADIUS:
Of course you can use RADIUS for authentication.
Just use the command "aaa new-model"
You will have to do 2 steps (used is a TACACS Server
but Radius will work the same, just Define a radius Server instead):
Step 1 (AAA Activation)
aaa new-model #Activates the AAA-Service
aaa authentication login default enable
aaa authentication ppp default local #or TACACS+
aaa accounting update periodic 5
aaa accounting network default wait-start tacacs+ #What Information the Router should send to the AAA-Server!!
2. Settings for Accounting Server #For Radius use "RADIUS-Server" instead of "TACACS-SERVER"
tacacs-server host "IP-Adresse"
tacacs-server key "Kennwort"
Hope that will help you!
Bye Matthias Steffens