ping

The ping command ‘‘bounces’’ a packet to and from a specified network host.

Format

The format for this command is:

 ping [-nqv] [-i wait]] [-s size] [-l preload] host

  where:

-i wait  Wait waitseconds between sending each packet. The default is to wait for one second between each packet.
-l preload  If preload is specified, ping sends that many packets as fast as possible before falling into its normal mode of behavior.
-n  Numeric output only.  No attempt will be made to lookup symbolic names for host addresses.
-q  Quiet output.  Nothing is displayed except the summary lines at startup time and when finished.
-s size  ICMP packets other than ECHO_RESPONSE that are received are listed. ‘‘Echo Replies’’ are displayed symbolically.
-v  Verbose output.  ICMP packets other than ECHO_RESPONSE that are received are listed. ‘‘Echo Replies’’ are displayed symbolically.

 

 

 

 

 

 

Functional Description

The ping command is used to verify ether net network connections and setup.

It makes use of a feature of the ICMP protocol, which is used by hosts and gateways for low-level administrative chores. Each ICMP host is required to respond to an ECHO_REQUEST datagram with an ECHO_RESPONSE. ECHO_REQUEST datagrams (‘‘pings’’) have an IP and ICMP header, followed by a time and then an arbitrary number of ‘‘pad’’ bytes used to fill out the packet. The command continues pinging until interrupted by a Control-C.

When using ping for fault isolation, start by pinging 127.0.0.1 (a universal self-address, by internet convention.) This verifies that at least the onboard setup is workable. Then, hosts and gateways further and further away should be ‘‘pinged’’. Round-trip times and packet loss statistics are computed. If duplicate packets are received, they are not included in the packet loss calculation, although the round trip time of these packets is used in calculating the minimum/average/maximum round-trip time numbers. When the program is terminated by a Control-C a brief summary is displayed.

Ping will report duplicate and damaged packets. Duplicate packets ‘‘should never happen’’: they’d have to be gateway problems. Tell your network manager.

Damaged packets (data doesn’t look like it should) are serious cause for alarm and often indicate broken hardware  somewhere in the ping packet’s path (in the network or in the hosts).

See Also:


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