SBS VPN problem

Posted on 2009-04-18
Last Modified: 2012-05-06

I have a VPN set up on SBS2003. XP client has a SBS connection manager installed. It works fine (gets connected and allows to access shares) when using a mobile 3G as an ISP on my notebook.

Same when using a home internet connection through an ADSL modem working in DHCP mode, where the client is connected without using a router. When I use a router however (linksys WRT54GL with newest Tomato firmware onboard or WRT54GC working as a DHCP in home network which is also a access point for wifi network) the VPN gets connected and authenticated to SBS, but in is impossible to ping the server nor access it or it's shares.

I have all possible passthroughs (e.g. PPTP) enabled on the router, as well as tried to put my client in DMZ or forward a complete range of ports to it. None of that helped. When a router is between ADSL modem and client it is only possible to connect, but accessing server or it's shares gives not results.

Please help!
Question by:pietia336
    LVL 7

    Expert Comment

    ADSL Modem with DHCP (Basically a router), then adding another router into the scenario?

    No good, you need to put the ADSL modem in bridge mode, so that it only acts as a pass through adsl modem and not a router, then your router will be the main.

    Author Comment

    Unfortunately that is impossible, as the modem is not a configurable device in any way as it is provided by ISP.

    In fact in my opinion it acts as a bridge now, as it only allows to connect one client to it - ISP's DHCP assigns ONLY 1 IP address!

    So I need to use router as a DHCP for local network, with ADSL modem connected to it's WAN port. However then I face the above mentioned SBS VPN issue.
    LVL 77

    Accepted Solution

    As mikeewalton stated, if the modem is a combined modem and router you either have to put it in bridge mode or not add an additional router. Having 2 routers (2 NAT devices) does not play well with PPTP.

    Another thought is the routers you are adding may not support PPTP/GRE pass through. Some do not, though I would be surprised if that were the case with those units.

    Another important detail is when the routers are in place, in what subnet is the client assigned an IP? If it is the same as the corporate network, such as both using 192.168.0.x  If the same the VPN client will connect but you will not be able to ping or access any resources as routing cannot take place. All subnets in each network segment between the client and host must be different.

    Author Closing Comment

    It was in fact a routing problem. Same subnets of the corporate and client side network. After changing them to e.g. 192.168.1.x and 192.168.16.x everything works fine. Thanks!
    LVL 77

    Expert Comment

    by:Rob Williams
    Glad to hear you were able to resolve.
    Thanks pietia336.

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