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Open Up Ports on CISCO 1941 Router

Hello I was wondering how do I go about opening up a port for a CISCO 1941 router?

I would like to forward port 25 to a certain IP Address on my network from the WAN

I have looked in the routers setup but I can't find any ports or options to setup ports.


5 Replies 5

Mark Malone

Hey if you want to forward ports open you use NAT heres and example of static port forward

ip nat inside source static tcp 21 21 ex
ip nat inside source static tcp 80 80 ex
ip nat inside source static tcp 443 443 ex

int g0/0
ip nat inside

int g0/1
descr WAN
ip nat outside

Thanks for the reply, is the format

ip nat inside source static tcp ITERNAL IP 21 EXTERANL IP 21 ex


Yes thats the format

ip nat inside source static <protocol> <inside IP address> <inside port #> <Inside Global IP or Interface> <External Portx>


Mark's answer is excellent. I am just giving additional info about that command.

That command actually do two functions.

1-When a packet comes from WAN to LAN, router replaces the destination address with the private address you specified in your NAT command.

2-When packet comes from your server going to WAN, router replaces the source address with the public IP which you specified.

So your server is also able to initiate a outgoing session even with private address as well receving incoming session.



Apart from commenst provided by Fellow friedns on this post.

Just have look on the below link for descriptive explanation of port forwarinding.

Hope it Helps..


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