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From: John Blight on 15 Jan 2010 09:36
We have an intermittent problem where external access to websites hosted on
one of our servers (Windows Server 2003) is being lost.


Thoughts and observations so far:

1. Gateway

I can consistently connect to our network through VPN using the same gateway.

SMTP traffic is successfully sent and received through the same gateway, and
forwarded correctly.


2. Internal access

Websites can always be accessed from within our LAN, so it would seem IIS is
serving the sites properly.


2. Potential VPN configuration clash

This server was configured as a VPN server just before Christmas. A second
network interface was added. I thought that perhaps the existing network
interface, to which http traffic is directed, was being isolated from
Internet-based traffic as a security measure. However, I would have thought
that, if so, the problem would be a consistent one, not intermittent.

HTTP traffic is still configured to be forwarded to the IP address of the
original network interface.


3. Event logs

There's nothing obvious in the Event Logs that suggests a problem.


4. Services

Lists of running services (created using 'net start') when external HTTP
access is working and not working are exactly the same, so there's no
evidence of a service stopping that would cause this problem. However, just
because a service is identified as having started, I suppose it doesn't
necessarily mean it's running properly.


5. Re-establishing Internet-based HTTP access

Rebooting the server seems to fix it.

Restarting IIS on on the server doesn't.



Does anyone have any suggestions as to how I might pursue this further?


With thanks.

From: Chris M on 28 Jan 2010 06:30
On 15/01/2010 14:36, John Blight wrote:
> We have an intermittent problem where external access to websites hosted on
> one of our servers (Windows Server 2003) is being lost.
>
>
> Thoughts and observations so far:
>
> 1. Gateway
>
> I can consistently connect to our network through VPN using the same gateway.
>
> SMTP traffic is successfully sent and received through the same gateway, and
> forwarded correctly.
>
>
> 2. Internal access
>
> Websites can always be accessed from within our LAN, so it would seem IIS is
> serving the sites properly.
>
>
> 2. Potential VPN configuration clash
>
> This server was configured as a VPN server just before Christmas. A second
> network interface was added. I thought that perhaps the existing network
> interface, to which http traffic is directed, was being isolated from
> Internet-based traffic as a security measure. However, I would have thought
> that, if so, the problem would be a consistent one, not intermittent.
>
> HTTP traffic is still configured to be forwarded to the IP address of the
> original network interface.
>

I think this is your problem. You have two network cards, are they both
connected to the same physical network, configured with the same default
gateway? You can only have one default route, so you have probably ended
up in the situation where traffic received on one network card is being
replied to via the other.

--
Chris M.
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