VPN keeps getting dropped almost every 10 mins.! Why?

[Exo]

Hi,

I have setup two VPN servers in my work environment.
The two servers sit behind a hardware firewall and
both machines are mapped to external IPs via NetScreen 25.

Each machine has two NICs and they both have Windows 2000
Server
installed (with all Microsoft's latest patches applied).
Internet
Authentication Service is installed and both machines
belongs to
a domain controller which provide authentication services
for these
VPN servers.

Since both machines have identical setup (except IP),
I will give you config of VPN Server1:

Two NICs:

NIC#1Public: 192.168.1.90 mapped to 202.15.15.90
SubNet MasK 255.255.255.0
Default Gtw 192.168.1.1
Preferred DNS 192.168.1.80

NIC#2Private: 192.168.1.92
SubNet MasK 255.255.255.0
Default Gtw(blank-per MS manual i found on the Internet)
Preferred DNS 192.168.1.80

Users are prompted for password and authenticated
with no problem but only stay connected for
about 10 to 15 minutes then gets dropped
eventhough they can reconnect with no problem.
This problem persist for every user trying to VPN in.

Can someone tell me if my configuration is correct?
What can I do to rectify this?

Any help on this would be much appreciated.

Thanks In Advance,

-Exo

 

[Chris Knapp]

Well, you can try disabling IAS. IAS is simply a RADIUS server that passes
authentication & accounting to the nearest AD controller. If you are using
Microsoft RRAS for your VPN solution, then you don't need IAS.