I'm trying to find a way to centralize user management & authentication for a large collection of Windows & Linux Servers, including network devices (Cisco, HP, Juniper). Options include RADIUS/LDAP/TACACS/... Idea is to keep track with staff changes, and access towards these devices.

Preferably a system that is compatible with both Linux, Windows & those network devices. Seems like Windows is the most stubborn of them all, for Linux & Network equipment it's easier to implement a solution (using PAM.D for instance).

Should we look for an Active Directory/Domain Controller solution for Windows? Fun sidenote; we also manage client systems, that are often already in a domain. Trust-relationships between Domain Controllers isn't always an option for us (due to client security restrictions).

I'd love to hear fresh ideas on how to implement such a centralized authentication "portal" for those systems.