# Authentication passing on Cisco ACS but failing on VPN Concentrator



## wansolutions (May 26, 2006)

G'day All, 
I am experiencing a problem where users, within a couple of NT domains, are being authenticated against the Cisco ACS server (RADIUS) then the same users are failing authentication on the VPN Concentrator. 
I am currently able to authenticate other NT domain users and AD users through the same ACS/VPN Concentrator pair. 
What's going on? 
The users that are passing on the ACS and failing on the VPN can be authenticated locally within the domain. 
When I try a test authentication against the authentication server configured on the Concentrator, I get the following message returned: 

Authentication Error: No response from server 

However the user is definately passed on the ACS server.


----------

