SBS2003 lan loses internet when vpn client remote desktops

[Dimm]

We have recently introduced a cisco 2800 router onto a small network with an out of the box SBS 2003 with pretty standard configurations for DC DNS DHCP RA.

The Cisco router is now handling DHCP for VPN and Lan clients. It has a pointer to the SBS DNS Server and to the ISP DNS. The router has 2 wans one ADSL and one to a Cable Modem. The cable modem is used for the vpn's

SBS DNS points at itself and forwarding has been removed.
SBS DHCP has been disabled
SBS Routing and Remote access has been disabled.

The VPN tunnels seem to go up ok. The only problem is that when vpn clients attempt to remote desktop sometimes it does connect without problems but normally first time in the day it fails to connect at the login screen.

The local lan loses all internet connectivity for around 10 minutes.

Normal service is then resumed. This also happens much less infrequently overnight once or twice without remote desktop sessions.

As an aside, one remote vpn client is on the domain and can see lan dns names whilst another is not on the domain and cannot see lan dns names but can use ip addressing without problem.

Has anybody seen anything similar to this as between the SBS and cisco there are an awful lot of variables. Any pointers?

 

[ShackDaddy]

I haven't seen this issue, but there are some things I would recommend about your setup. Only have your router configured with the internal SBS box's IP for DNS, and DO configure your SBS box to use your ISP's DNS servers in the DNS forwarding tab in the DNS Admin tool.

If, for one reason or another, your clients (either VPN or internal) end up querying an external DNS server when looking for internal info, all sorts of screwy things can happen, so it's best that clients not have access to the IPs of those external DNS servers, and instead only be given the SBS box address for DNS.

When does the local LAN lose connectivity?

And what is the endpoint for the incoming VPNs, the server or the Cisco device? I assume the latter.




Dave Shackelford
Shackelford Consulting

 

[Dimm]

Dave

Thanks for that, the vpn terminates at the Cisco. The Cisco is eventually going to host an ip telephone system, we are not 100% privvy to its set up and assume that it's DNS is required for this, but what you say makes perfect sense to me although external dns lookups seem to perfom a lot quicker from the Cisco.

The lan looses connection at pretty much random times throughout the day, and always for aout 10 minutes. Starting a remote desktop session will normally trigger a ten minute outage.