DrayTek Vigor 2800
To enable pings (ICMP echo request/response) follow the steps below.
Login to the router using your web browser. (Type http://192.168.1.1 (default is 192.168.1.1) in the address field of your browser, and then press Enter).
The default username and passwords for the login screen are blank.
Once logged in on the left you will have a menu, scroll down to the "System Maintenance" section and select "Management".
In the "Management Access Control" section locate the checkbox "Disable PING from the Internet" and make sure it is NOT ticked and then press "OK" to apply the setting.
The above procedure is documented in the user manual (pdf, 5.1 MB) on page 155, this includes images of the web interface.
You may also find the quick start guide (pdf, 1.1MB) on page 17 useful when connecting to your router.