Enabling port 25 on a Cisco 837 router

Unanswered Question
Apr 4th, 2007

Hi. I need to enable port 25 on a Cisco 837 router and redirect it to an internal mail server. The server is currently using Exchange 2003 and it's role is changing from picking up POP mail to having SMTP mail directed to it. I'm OK with getting the MX records redirected but need help in setting up the router to allow this. The OS is 12.3(8). Thanks.

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fedefalchi Wed, 04/04/2007 - 12:13

Hi rexbiesty,

why do you try using NAT? I think you had only one valid IP address, ok?

Following basic configuration for router:

Exchange 2003=

IP external router=

In global mode:

ip nat inside source static tcp 25 25 extendable

on interface eth0 (inside)

ip nat inside

on interface s0 (outside)

ip nat outside

See you

Rex Biesty Thu, 04/05/2007 - 00:28

Hi Fedefalchi

I tried your solution (i've substituted the real private and public IPs for the ones in your example) but got this error

ip nat inside source static tcp 10.^1.1.1 25 extendable

% Invalid input detected at '^' marker.

I've included the config. This site does have a static IP but it doesn't seem to be hard wired in the router. The site uses ADSL for it's internet access.

Rex Biesty Thu, 04/05/2007 - 00:53

Sorted. Used this command instead

ip nat inside source static tcp 25 interface Dialer0 25

Thanks for your help.


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