In Ch. 13 of the CCNA Routing and Switching ICND2 200-105 Official Cert Guide, Table 13-5 describes likely general causes for a ping failure based on the line/protocol status.
Create a 2- to 3-page troubleshooting guide based on this table of ping failures. For each state combination, list the steps you would take to further understand any problems at each appropriate layer and verify that your configuration is correct. Make sure your steps are logical, clear, and appropriate for WAN protocol.