NAT - Port Forwarding

[pmesjar]

Hi guys, I got one more theoretical question. I'm newbie when it comes to NAT. Right now I'm configuring my first NAT examples in my lab (Cisco 2500 series routers, 12.0 IOS images). While I was doing some "internet" research on the topic, I could not find the right answers to my questions. I would like to know more what is behind the mask of port forwarding, what it is used to, when it is useful to implement it and how to configure it. Or if you can point me to any documentation on the net, I would be more than grateful.

Thank you all in advance Peter Mesjar
CCNA, A+ certified
pmesjar@centrum.sk

 

[ChrisAC]

Port forwarding is used to take incoming traffic to the IP address of the device that is to be configured for port forwarding (ie. the router) and forward that traffic to a specific internal IP address. For example, I have a single static IP address on my router and I port forward port 3389 for Microsoft RDP to my desktop to that I can reach it from the office.

ip nat inside source static tcp 192.168.100.5 3389 interface ATM0.1 3389

This takes port 3389 traffic into interface ATM0.1 (my ADSL card) and forwards it to my desktop. I also add an access list to make sure that only I can get to my home PC from work.

access-list 105 permit tcp host <my work IP> any eq 3389 log
access-list 105 deny tcp any any eq 3389 log

For more information look at

http://www.cisco.com

and search for &quot;port forwarding&quot;.

Chris.
**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[ciscojunk]

Hi Guys,

I am sure I can add &quot;extendable&quot; at the end of this command
ip nat inside source static tcp 192.168.100.5 3389 interface ATM0.1 3389 &quot;extendable&quot;

Anyone know what purpose it serves

 

[pmesjar]

Thank you Chris Peter Mesjar
CCNA, A+ certified
pmesjar@centrum.sk