C:\>ping www.comptia.ca Unknown host www.comptia.ca
ping fails, you need to verify that the
ping is being sent to the correct remote host. If it is, and if name resolution is configured, you have to dig a little more to find the problem. This error might indicate a problem with the name resolution process, and you might need to verify that the DNS or WINS server is available. Other commands, such as
dig, can help in this process.
The Expired TTL Message
The Time to Live (TTL) is an important consideration in understanding the
ping command. The function of the TTL is to prevent circular routing, which occurs when a
ping request keeps looping through a series of hosts. The TTL counts each hop along the way toward its destination device. Each time it counts one hop, the hop is subtracted from the TTL. If the TTL reaches 0, the TTL has expired, and you get a message like the following:
Reply from 18.104.22.168: TTL expired in transit
If the TTL is exceeded with
ping, you might have a routing problem on the network. You can modify the TTL for
ping on a Windows system by using the
ping -i command.