NAT Question/Problem

Posted on 2003-11-27
Medium Priority
Last Modified: 2010-04-11
Ive got one machine connected to my cable modem with two nic's running ics, this machine is connected to a hub. on my internal lan i have a server running a pop3 and an smtp server. I also have a laptop i use at home as well as on the road. My problem is, when i check my email at home, i use the internal lan ip of the server. When away, I use my public ip, and the ics machine is set to forward to proper ports to my server. When im at home, if i try to connect to my public ip address, the ics machine doesnt forward the request properly. I can ping the public ip from the internal lan fine, but cant connect to the server. I cant remember if my linksys router translated the request properly or not since i fried my wan port. Does anyone know how to make this work? the problem is every time i change the server ip in outlook express, it ends up downloading double messages.
Question by:alfer

Assisted Solution

Robing66066 earned 93 total points
ID: 9834610
From a networking perspective, I think you have two options.

The first is for you to set up a VPN on your ICA box and when you are on the road, connect to the VPN and then to your pop3/smtp server from the inside at all times.

The other is to add a hub where you plug the outside interface of your ICA server into along with your cable modem.  You would then plug your laptop into the same hub when you were at home.  It would give you an outside address (from the perspective of your internal network).  You could then connect to your pop3/smtp server through the outside at all times.  

As for connecting to the outside address from your inside network, routers doing NAT won't let you go in and out again the way you want it to, so I don't think you'll get that to work.

I am kinda surprised that your outlook express is giving you double messages.  Maybe this is more an outlook problem than a network problem.  You might be able to avoid the problem by using the 'leave a copy of the mail on the server' option or by creating more than one profile.

Good luck!
LVL 31

Assisted Solution

rid earned 93 total points
ID: 9835233
I agree with the "more than one profile" idea. I have basically the same problem: laptop owners need to check their mail at  the office and they want to be able to check mail from home. Mail server is behind router running NAT. I propose to set up two profiles or two "accounts" even, in the mail clients. One for "Mail at work" and the other for accessing mail from their homes. Most proper mail client programs should handle this neatly.

Assisted Solution

drev001 earned 93 total points
ID: 9839974
Do you have a static IP address? if so, does it have a dns record associated with it? Find out by running ping -a ipaddress. This will resolve a host name to it. Use this host name instead of the ip address within outlook express. Next you'll need to install a free DNS server on the ICS machine (such as Posadis DNS Server) Create a zone on the DNS server for the domain attached to the static IP's host name then add the relevant A record but point it to the ICS machines internal address. Also configure forwarders to the isp's dns servers.

On the laptop specify the internal dns server as primary and your isp's dns server as secondary. This sounds long winded but will work if you're determined.

Accepted Solution

TIMFOX123 earned 96 total points
ID: 9844476
You may want to go to dyndns and get a static name with a dynamic ip address.  Then refer to the static name.  it is free and works great.  You can also advertise a webserver with this name.  They also support MX records.


Author Comment

ID: 9844481
yeah i actualy use both dhs.org and yi.org for that. Thanks for all the help guys but none of the solutions did really what i was looking for. after some searching I found what i needed using kerio's winroute pro. Their advaced NAT settings did the trick, finally. Thanks for the help anyway...

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