Port Forwarding on Cisco 881

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Dec 2nd, 2011
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I have my Cisco 881 router up and running, routing all traffic on my small network. I am wanting to utilize port forwarding to enable FTP (forward port 21). All docs I have found say you need to be running Configuration Professional (not Express) to do this. Please advise.

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Daniele Giordano Fri, 12/02/2011 - 11:28
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The cisco 881 is a IOS based router.
You can use command line interface to configure port forwarding.
Connect to the router via telnet or console.
After login use configure terminal to enter in configuration mode.
Use this command to enable port forwarding:
ip nat inside source static tcp "inside local ip" "external ip" 20 extendable
ip nat inside source static tcp "inside local ip" "external ip" 21 extendable
ip nat inside source static tcp "inside local ip" "external ip" 1020 extendable


e.g.

router name(conf)# ip nat inside source static tcp 192.168.1.20 85.85.85.45 21 extendable


You must open all necessary port according to FTP modality (passive or active)


Regards.

David Block Fri, 01/17/2014 - 12:46
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Why are you throwing port 120 into the mix? FTP is 20 for Data and 21 for commands.


Here is what i enter on my 881W to enable FTP to an internal server (192.168.1.77) with port forwarding from my DHCP internet connection:



ip nat inside source static tcp 192.168.1.77 20 interface fastEthernet 4 20
ip nat inside source static tcp 192.168.1.77 21 interface fastEthernet 4 21


ip access-list extended OUTSIDE-->IN
permit tcp any any eq ftp
permit tcp any any eq ftp-data
no deny ip any any log
deny ip any any log

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