FAX On-Ramp over VPN

[Cristian Iconaru]

Hi guys,

have anyone tried configuring fax on-ramp over VPN?

If so, how have you managed to send the fax over the tunnel?

Thanks.

Regards

[Steven Holl]

VPN shouldn't matter.  As long as you have L4 connectivity from the router to the SMTP server, you should be fine.

[Cristian Iconaru]

Hi Steven,

L4 connectivity is ok. The fax works without a vpn (I used the smtp server's public IP).

but when I try to send it over VPN, I want to use the server's private IP and force the traffic through the tunnel, this doesn't work. I get the no route to host error message. I believe this is normal when the gateway terminates the VPN tunnel and also tries to send the fax-email (the source ip of the packets is public - gateway's public ip - and the destination is private - smtp server -).

What do you think?

Thanks.

Regards

[Steven Holl · Accepted solution]

It sounds like the SMTP traffic towards the SMTP server's private IP is going out your public interface instead of the tunnel?  From the router, if you telnet to on port 25, does a connection open up?  If not, you have a L4 issue, which it still sounds like is the case and you can isolate the issue from being specifically a T.37/SMTP issue.

Is your NAT ACL for interesting traffic configured to match traffic sourcing from the router to the private IP of the SMTP server?  I don't think there is a way to bind SMTP traffic from the router to a specific interface, so it should source off of whatever interface is closes to the L3 destination IP in the route table.  Traceroute to the SMTP server IP will shed more light on what network the router will use for the source IP.

[Cristian Iconaru]

Hi,

I think matching the traffic sourcing from the router to the private ip of the smtp server will do the job.

I will try it tomorrow, see what happens.

Thanks.

Regards

[Cristian Iconaru]

Hi,

matching the router generated traffic to the smtp server private IP did the trick.

Thanks.

Regards