I am having username and password of my router how can i ping the router

If you are using a computer on the LAN, you need to ping the routers internal address. If you are using a computer that isn't on your network, you need to ping the router's WAN address.

Click here from your computer to find it's current WAN address.

http://www.whatismyip.com/

Also, be sure that ICMP/Ping is allowed (turned on) in your router.