Asus routers like the RT-N66U have support for SNMP in the latest firmware. Here is how to enable and test it (here using the awesome Asuswrt-merlin alternative firmware ).
Go To Administration and click on SNMP. Enable SNMP, enter a system name, system location, SNMP Get Community (just any text, this acts like a password). Click on Apply to activate the changes.
To test if SNMP is working you can use the snmpwalk command. If your router IP address is 192.168.1.1 and your SNMP Get Community string is ‘public’, run
snmpwalk -Os -c public -v2c 192.168.1.1 iso.18.104.22.168.1.1.1
The output should look like “iso.22.214.171.124.126.96.36.199 = STRING: “Linux RT-N66U 188.8.131.52 #1 Thu Nov 20 13:57:15 EST 2014 mips” if SNMP is working. If it is not working you will receive a message like “Timeout: No Response from 192.168.1.1”.
To get more data from SNMP run ‘snmpwalk -Os -c public -v2c 192.168.1.1’