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Outlook VPN Connectivity

Posted on 2007-12-06
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Hi all,

I have a persistent hardware VPN tunnel which links a remote office to the main office. I cannot connect outlook clients over RPC as the exchange server uses a different gateway, not the hardware VPN router. I had planned to use RPC over HTTP however after attempting to implement it, i cannot get the machines to connect via HTTPS - all I get it the DIrectory Services via TCP to the DC (uses the VPN router gateway). I cannot seem to get it to use HTTPS only despite having both Fast and Slow boxes checked. I've installed the internal SSL certificate to the remote machines and can authenticate to the RPC directory. Any ideas?

Thanks,
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Question by:lsmi4126
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by:SteveH_UK
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For the tunnel VPN, you should add a persistent route.  This tells Exchange where to route traffic to for the connected network.  You should add this route to all your servers, since your VPN gateway is not a default gateway.

Use the ROUTE command.

See http://technet2.microsoft.com/WindowsServer/en/library/31bb32f5-99b7-4685-9542-24337b5deb401033.mspx
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SteveH_UK earned 500 total points
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For the HTTP/RPC solution, there is a lot of info around, but we'd need to answer your issues in stages.  If the IPsec route is fine, then let's leave it there, otherwise ask away!
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by:lsmi4126
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Thanks for the info. I don't have a 2K3 box at the remote location - just a VPN router (dlink) which creates the tunnel with another identical VPN router in the office - ie the VPN tunnel terminates before any software. If i add the persistent route to the exchange server, how is this going to help requests going through the hardware VPN gateway getting to it??

I have managed to get RPC/HTTP going - it just takes a while to connect everything other than the DS through TCP. If I can get everything going down TCP it would be good though!!
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by:SteveH_UK
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The problem I am trying to address is as follows:

Branch office:  VPN router, clients
Main office:      Servers, Exchange default router, VPN router

I'm assuming that the VPN is operating a standard IPsec tunnel VPN.  Other systems will change the way things work.  A tunnel VPN enables routing between two disconnected networks.  It should not put clients in the local subnet, as it is unaware of clients.  This is not the way mobile VPNs work, such as PPTP, L2TP/IPsec, and some firewalls.

Your clients connect to Exchange via the VPN router.  This all works fine and Exchange receives the request.  However, when Exchange replies, it replies to the original address of the client.  The route it chooses is not the VPN router, but its default route.  The default router does not know how to route the packet and the client never receives it.  Therefore, you need to instruct the Exchange server, and other servers, to direct packets to the branch network subnet via the VPN router.

Note also that the branch office subnet and the main office subnet must not overlap, otherwise you will have routing problems.

You use the ROUTE command like this:

ROUTE ADD [Branch Office Subnet] MASK [Branch Office Subnet Mask] [Main Office VPN Router IP Address] METRIC 1

This will enable replies to clients to be sent through the VPN router.
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