The ping command
 


The Cisco ping command uses, by default, the output interface’s IP address as the packet’s source address, unless otherwise specified in an extended ping.

Ping response packets (ICMP Echo Replies) reverse the IP addresses used in the received ping request to which they are responding.

The danger when troubleshooting with the standard ping command is that routing problems can still exist.  A more thorough alternative is to use the extended ping command to act like you issued a ping from a computer on that subnet, without having to call a user to ask to enter a ping command for you on the PC.  The extended version can be used to refine the problem’s underlying cause by changing several details of what the ping command sends in its request.  When a ping from a router works but a ping from a host does not, the extended ping could help you re-create the problem without needing to work with the end user on the phone.