Question

VPN Client access to ISA with multiple external IP

Asked by: P-R-W

Hello,

I have ISA 2006 installed with 1 IP address on the external NIC. When I have VPN Client enabled (PPTP) I can connect and everything works fine. My ISP gave me a block of IP adresses and I have added an extra IP address to the external NIC. IN ISA this is recognised beacuse I can publish a server to the second IP address. But VPN Client doesn't work anymore. I cannot connect to first or to second IP. I cannot find a setting where I can explicitly say that VPN Client should listen to IP address 1. Does anybody know?

Thanks

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Asked On
2009-06-05 at 05:30:04ID24466747
Tags

ISA VPN CLIENT

Topics

Network Software Firewalls

,

MS Forefront-ISA

,

Virtual Private Networking (VPN)

Participating Experts
2
Points
500
Comments
15

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Answers

 

by: pwindellPosted on 2009-06-05 at 08:01:56ID: 24557137

Added the extra IP# for what?  It does not sound like you have a real reason to do that.

You should never add multiple IP#s to the ISA without a solid and specific reason to do so.

However that should not break the VPN in any case.

You can not select a specific IP to receive VPN Connections,...you can only select the Network Definition,...which is almost always going to be External.

Even though it is not supposed to be so,...sometimes changes do not work correctly until the ISA is completel rebooted.

 

by: keith_alabasterPosted on 2009-06-05 at 11:09:33ID: 24558882

Adding the second IP is fine (I have about 16, one for each service I publish) - and is common practice although not really for VPN headers.

You can select any IP that you want to act as the VPN header as you decide it when you launch/configure the vpn client. If you have two ip addresses on the ISA external nic then both of these constitute the EXTERNAL listener - and the VPN should respond on requests on either IP. What you cannot do is select to listen on only one ip address - for VPNs anyway.

Pwindell is correct about reboots. As changes to the VPN config likely will make changes to the RRAS service, it requires a reboot although this is not always the case.

 

by: P-R-WPosted on 2009-06-06 at 02:14:43ID: 24562371

It is important to have additional IP addresses on the external interface. I will have to publish two the same services so on two different IP's. Had restarted the firewall service. That did not work. Have restarted the ISA server, this also didn't resolve it. What I did see was that when I do ipconfig I see the following:

IP: x.x.x.179
SM: 255.255.255.248
IP: x.x.x.178
SM: 255.255.255.248
GW: x.x.x.177

178 was the first IP and I added 179. Why is 179 standing on top? Is that a problem? Everything seems to work OK. SMTP was going to 178 and still does. Why is VPN Client giving a problem?

 

by: P-R-WPosted on 2009-06-06 at 03:07:36ID: 24562535

Saw in the logfiles that there was a Failed connection Attempt on the system rule: Allow VPN Client traffic to ISA server. I haven't changed anything to this rule and had a look: you cannot realy change anything either. I have disabled the VPN Client access then I get a denied connection. When I enable it again I get again an Failed connection attempt...

 

by: keith_alabasterPosted on 2009-06-06 at 04:34:56ID: 24562698

 

by: P-R-WPosted on 2009-06-06 at 07:37:19ID: 24563143

Thanks for BPA suggestion, but already tried it and doesn't give me any errors

 

by: keith_alabasterPosted on 2009-06-06 at 10:00:28ID: 24563546

None at all? Thats a first I think in more years than I can remember.
The fact that it is working with just one address successfully suggests ISA is set up fine.
If all you have changed is to add a second public IP address and changed the subnet mask the ISA won't give a stuff about that and nor should the host OS.




 

by: P-R-WPosted on 2009-06-06 at 10:02:57ID: 24563553

You're right there are some errors/warnings :-). But it doesn't give me errors that I can relate to the change i made.

 

by: keith_alabasterPosted on 2009-06-06 at 10:07:51ID: 24563571

just as a test, with both addresses assigned to the ISA, have you tried making a vpn connection to both ip addresses?

I've just tried mine and both connect successfully.

 

by: P-R-WPosted on 2009-06-06 at 10:19:49ID: 24563615

Yes i did. Both gives me same errors. To give you full specs:
Before change everything works fine:
external IP: 212.x.x.178
dmz: 172.16.0.1
internal: 192.168.17.1

Have a site-to-site VPN and several servers published (SMTP, RDP, HTTP)

After change:
Have added extra external IP address to external nic: 212.x.x.179
Subnet mask was 255.255.255.248 for 1st Ip (via ISP) so also gave second IP same subnet mask.

Idea is to connect via PPTP to IP1 to go to internal network and publish PPTP as a service to second IP address so that VPN traffic from supplier would go to my DMZ. Have created the rule but when VPN client to internal didn't work anymore I have deleted the publish rule to DMZ. Is it possible something was left behind?

Everything else still works fine (site to site and other published servers).
 

 

by: keith_alabasterPosted on 2009-06-06 at 10:23:41ID: 24563636

But the site-to-site vpn is working OK even with the new IP address?

 

by: P-R-WPosted on 2009-06-06 at 11:02:29ID: 24563767

Yep, site to site is fine. When I publish PPTP on external network I can specify that it should listen on 212.x.x.179. Is there something like that for VPN Client Access? I found the system rule (automatically created) and this one you cannot change. External is external and you cannot identify which IP address ...

 

by: keith_alabasterPosted on 2009-06-06 at 11:11:59ID: 24563810

Correct - as I pointed out earlier.

Let me have a further look at my own system. What I don't have is two different VPN's so let me investigate a bit.

 

by: P-R-WPosted on 2009-07-01 at 06:59:38ID: 24754364

The problem lied in the order of configuring. When you first publish PPTP and the add external IP it doesn't work anymore. Even when you disable the publish rule. I cleared the whole config and started from scratch. First extra IP adresses on external. Then VPN client access. After that publish of the PPTP server on the second external IP. This works now. Found the solution in:

http://www.winserverkb.com/Uwe/Forum.aspx/isa/4460/Bizzare-ISA2004-VPN-Issues-Please-help

Keith: thanks for the time you have put in. Therfore you get the points

 

by: keith_alabasterPosted on 2009-07-01 at 10:43:16ID: 24756532

Neat - and good detective work - thanks for the update :)

20120131-EE-VQP-002

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