It sends four ping requests in the default setting. With the -n option, you define the desired number of ICMP echo requests. The computer name will be displayed to you along with the ping statistics in the terminal. Use the ping command with option -a and the target computer’s IP address in order to determine the target’s host name. This is called a continuous ping (see tip below). With option -t, the addressed target computer is pinged until you end the procedure with Ctrl + C to display the ping statistics. With a TTL of 58, for example, you can assume that the response packet was dispatched with an initial value of 63 and passed five network nodes on the way back. The TTL that you receive as output normally corresponds to the responding computer’s initial value minus the number of hops on the route. Should the TTL drop to 0, the data packet is rejected. The TTL is reduced by 1 by every network node that the data packet passes. Usually, implementations have an initial TTL of either 31, 63 or 127. The initial value amounts to a maximum of 255. The validity period specified as the TTL corresponds to a data packet’s elapsed time. The response time specifies how long a data packet requires to be sent to the target computer and back. Validity period for ICMP packets (time to live, TTL) (only with IPv4).The ping command delivers the following information as output: If there is no response from the router, it can be assumed that the computer is in fact available but is not automatically responding to the echo request due to its configuration. Normally in this case a router responds that either the network or the appropriate host is not available. If the addressed target computer doesn’t respond, ICMP provides a notification from the appropriate gateway. As a result, the unavailability of the target computer cannot be inferred from an unanswered ICMP request. In practice, this doesn’t always work, as many administrators, for security reasons, configure the computers they manage in such a way that ICMP packets are rejected without a response. In theory and in accordance with the protocol specification, computers that support ICMP and/or ICMPv6 must automatically respond to incoming echo requests with an ICMP echo reply. For computer networks using IPv6, ICMPv6 has a successor protocol that can be used for this purpose. ICMP (Internet Control Message Protocol) is a protocol that enables the exchange of information and error notifications within IPv4 networks. In order to verify a computer’s availability, ping sends in its default setting four ICMP echo request packets of 32 bytes each to the address assigned as a parameter.
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