Asus DSL-N11 - Manual (Page 32)

 DSL-N11 Chapter 5: Troubleshooting
5. After restarting the router, why is it that I see different WAN IPs in MS
DOS and in the router configuration page?
This is normal. The interval time between the ISP DNS server and ASUS
DDNS results to different WAN IPs in MS DOS and in the router configuration
page. Different ISPs may have different interval time for IP updating.
7. Is the ASUS DDNS service free, or is it just a trial version?
The ASUS DDNS service is a free and embedded service in some ASUS
routers. Check your ASUS router if it supports the ASUS DDNS service.