How to enable mirroring on Asus RT-N66U

If for the purpose of troubleshooting etc., you need to mirror on the Asus RT-N66U [Asus Dual-Band Black Wireless-N900 Gigabit Router - RT-N66U (Google Affiliate Ad)] you'll find no easy switch in the control panels.  Fortunately I found a PDF here that includes a couple commands on page 2 that do the trick nicely.

First, you'll have to telnet into the router, or access it's system command console here:
https://xxx.xxx.xxx.xxx:8443/Main_AdmStatus_Content.asp
(Insert your IP instead of the 'xxx's.  Also, I have mine set for secure access on port 8443)

Then issue each of these, followed by enter.  The console will provide no feedback.

iptables -A PREROUTING -t mangle -j ROUTE --gw 192.168.1.40 --tee

iptables -A POSTROUTING -t mangle -j ROUTE --gw 192.168.1.40 --tee

"The above commands will make a copy of all of the traffic on your network to the
gateway IP address 192.168.1.40", for example.

When done, to switch off mirroring, use:
iptables -F -t mangle

"The above command will flush the 'mangle' table and stop mirroring traffic to IP address
192.168.1.40 without rebooting the router."

Special thanks to Bill Parker for that info!


Asus Dual-Band Black Wireless-N900 Gigabit Router - RT-N66U (Google Affiliate Ad)