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CISCO 2811, NAT and Exchange Server 2003 Problem

Posted on 2009-04-10
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Last Modified: 2012-05-06
Hi!!!
This is my first post in this forum hoping to find a solution to the problem I am facing with a CISCO 2811 router.
First of all, I have to mention that I am not familiar with Cisco routers but I have to work it out because I am the only IT person in the company I work.
The problem:
I have a CISCO 2811 router, IOS Version 12.4(15)T1 and I administer it with SDM Version 2.5.
In this router there are three ADSL interfaces of which only one of them is enabled.
The ISP gave me a range of 17 IPs and I use them in order to "publish" some of my servers to the Internet.
One of those servers is my mail server (MS Exchange 2003) which is playing both the roles of frontend and backend server.
Using SDM and the NAT Configuration Interface I have created some static rules for this server translating addresses and ports.
For the exchange server I redirect  ports 25,110,443, and 80.
Now, the problem is that when I  NAT port 25, my server can accept incoming mail but cannot send outgoing email. All the outgoing emails are stuck to the server's queue.
Running Microsoft's SMTPdiag utility in my mail server I can see that there are no errors with the communication with other servers.
When I NAT the addresses without port redirection, which means that all the ports are free then the problem disappears.
I have no access problems with ports 80 and 110 with the same server.
This is really weird and i do not know if this is has to do with the router or the server.
When I did exactly the same thing with the same server using another line connected with a 1721 router, everything worked fine.
I would appreciate if anyone could suggest anything in order to find a solution.
I am attaching the configuration of my router.
Thank you very much in advance.
Nikos
   
2811-problem.txt
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Question by:gloec
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JFrederick29 earned 500 total points
ID: 24115246
The problem is that port redirection is only for inbound traffic and you have no outbound NAT configured on the router.  Either go back to the  1-1 NAT or add this to the router:

conf t
access-list 1 permit 10.x.x.x 0.0.0.255    <--your LAN range
ip nat inside source list 1 pool DOT overload
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Author Closing Comment

by:gloec
ID: 31568883
Thank you ever so much for your help!!!
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