I'm looking at different 5505 and 5505 bunldes. One is licensed for 10 users (pretty cheap), the other one is licensed for 50 users (considerably more expensive). My question is - what do those numbers actually mean? Is this the limit of users that can be configured in the AAA authentication mechanism or does the ASA check how many IPs are connected to it?
In case the previous responses were not quite explicit, you can configure as many users as you wish. The limit that the ASA imposes is the number of devices connected at the same time.
The ASA tracks IP addresses on its inside.
for example if you purchase 10 user bundle licenses, it means that the ASA can only build xlate connection (allow connection) for only 10 ip addresses and no more.
i suggest you go for
ASA 5505 Unlimited User Software license - ASA5505-SEC-BUN-K8.