Enabling port 25 on a Cisco 837 router

[Rex Biesty]

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.

[fedefalchi]

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= 192.168.1.254

IP external router=10.1.1.1

In global mode:

ip nat inside source static tcp 192.168.1.254 25 10.1.1.1 25 extendable

on interface eth0 (inside)

ip nat inside

on interface s0 (outside)

ip nat outside

See you

[Rex Biesty]

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 192.168.1.254 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]

Sorted. Used this command instead

ip nat inside source static tcp 192.168.1.254 25 interface Dialer0 25

Thanks for your help.