Fortigate to Fortigate VPN with ISA on one side. =\

Posted on 2008-11-19
Last Modified: 2012-06-27

Need to design a persistent VPN between two Fortigate units (easy part)  

Main site has an ISA 2004 firewall installed on SBS 2003 connected to a Fortigate 60.
SBS Box is the gateway for the site and utilizes ISA for rules to govern clients that is not possible on the fortigate with its AD integration thus cant be removed. ( for Fortigate/SBS side of network and for internal)

Secondary site is just a network of PCs no server with a Fortigate 50. (

We have setup a IPSEC vpn between the two fortigates which seems to be connecting fine, from the remote site, we can ping the DMZ (reason for this) interface of the foritgate on the remote site.

We spoke to our Fortigate Distro tech support and they advised that pushing a vpn through isa can be tricky so to "sidestep" it by pushing the VPN out of the DMZ on the Foritgate 60 which would be connected to the internal LAN. Done this and connected up DMZ to internal lan with IP address

Pings and tracert's to from the remote site is successful, anything else on the network fails, i think because the gateway for these devices is isa?

So i went to work on setting up a route in ISA to push traffic aiming at the remote site ( to use (dmz) as the gateway.

ISA Route Table:

Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
     20      1      1   <- ADDED ROUTE     10     10     50     10     20     20     20     10     20      1      1
Default Gateway:
Persistent Routes:

This i would have imagined would have fixed the issue but alas no.

Tracert to 192.168.8.anything gives Dest Host Unreachable instantly.

I would have expected a tracert to say - reported dest host unreachable if the routing in the fortigate was stuffed up.

I dont know ISA too well so any assistance would be great.
Question by:Superdata
    LVL 7

    Expert Comment

    Everything seems fine. Try adding this same route in one of your internal clients and try tracing to remote site (so it wouldn't go through ISA) and see what happens.
    LVL 1

    Author Comment

    Sorry for the delay in this one, waiting for another fortigate 60 to turn up, other one had to put out into production so cant test with it. Should have an answer on Monday with how that bit went.

    IF that does work, then what will be required to fix my problem on ISA

    Or does someone have another solution on how to better bypass ISA?
    LVL 1

    Author Comment

    ok, tested,

    If i added a route to my PC it worked fine, however this is not really a solution, i need to get the server to recognise the route for all clients and itself obviously.

    Anyone have any idea why the route on the server isnt working? (i have a feeling ISA needs to be adjusted in some way?)
    LVL 7

    Accepted Solution

    OK, problem is somewhere within ISA. Try this: Configuration, networks, internal, properties, addresses, you should have all your internal subnets listed there (including remote). Check this first.
    LVL 1

    Author Comment

    ok added that in and now have some connectivity.

    I can RDP from the server to PCs on the remote side of the VPN, i can access folders and ping from local PCs to the remote PCs but not RDP, strange?

    Also from the remote site can access the server via RDP, access folders, but having some issues with Outlook syncing with Exchange. most of it is only capable by IP Address.

    Do i need to add group policy to add the windows route to all PCs or should the gateway (the ISA Server) be enough?

    Exchange issue: can find the exchange server but doesnt proceed "cannot open you default email folders. you must connect to Microsoft Exchange with the current profile before you can synchronize your folders with your offline folder file." (i am trying to open my mailbox on a laptop on the remote side)

    Do i need to configure DNS forwarding on the vpn to have hostnames resolve correctly across the VPN or whats the story here?
    LVL 7

    Assisted Solution

    DNS doesn't care about VPN. If your DNS servers are at the central office, you should simply point your remote clients to use them, nothing special to do about it (but from your symtomps, I would say that you have something misconfigured).
    About RDP problems: create ISA rule that would allow all From internal networks to Internal networks.

    LVL 1

    Author Comment

    Once i added Domain suffix and dns settings into the DHCP of the Fortigate most of it sprang to life.

    Will try the Internal to Internal in ISA, makes sense.

    Thanks Dusan :)

    Featured Post

    Live: Real-Time Solutions, Start Here

    Receive instant 1:1 support from technology experts, using our real-time conversation and whiteboard interface. Your first 5 minutes are always free.

    Join & Write a Comment

    There are several problems reported according slow link speeds or poor performance in TMG 2010, UAG 2010 or ISA 2006. I want to collect here some of the common issues together to give a brief overview what can be the reason. Nevertheless, not all of…
    Secure VPN Connection terminated locally by the Client.  Reason 442: Failed to enable Virtual Adapter. If you receive this error on Windows 8 or Windows 8.1 while trying to connect with the Cisco VPN Client then the solution is a simple registry f…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

    755 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    19 Experts available now in Live!

    Get 1:1 Help Now