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Forwarded ports not available from LAN with public IP

I have an 1811W router that I recently configured with NAT mapping ports 80 & 143 on the public IP address to the web server on the private network. If I try to access the mail server or IMAP email from a PC on the LAN using the domain name for the public side, I am unable to access it. I don't know if this is a firewall issue or a NAT issue. I took out the firewall entry that was denying traffic from the internet with an address on the LAN subnet but still have the same problem. I am able to access the web page and email server if I use the LAN IP address for the server, but there are two laptops that need to be able to access email from both the LAN and the internet, depending on where they are being used. I don't want to have to change the email setup every time it is taken out of the office. Any suggestions? (I thought of a DMZ as a possible solution, but I have a Samba share on this server that I need LAN access to and didn't want a terribly complicated configuration.)

2 REPLIES

Re: Forwarded ports not available from LAN with public IP

This problem can be addressed by a feature called NAT on a stick. Hope you have the needed IOS to support this. But, this doesn't address the DNS problem and you may have to use a host file or local DNS if name resolution is the problem.

Use this link to learn/configure. Post any follow up questions on the forum.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094430.shtml

HTH

Sundar

Bronze

Re: Forwarded ports not available from LAN with public IP

Sundar is absoloutly right it is a NAT issue.

And unfortunatly you won't get around it without having a terrible complicated configuration. Another thing to notice is this note "The router must process switch every packet due to the loopback interface. This degrades the performance of the router."

So unless you install a local DNS server, you are stuck with either Nat-on-a-stick, or changing the setup on the 2 laptops from time to time.

Sorry.

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