PING(8) PING(8) 990412 NAME ping - send ICMP ECHO request packets to network hosts SYNOPSIS ping [options] host [length [count]] Flags: [-c | -f] [-F] [-Q] [-LR] [-a] [-mnqv] [-dr] Options: [-l length] [-k count] [-p preload] [-D pattern] [-T tos] Options: [-b netbits] [-g gateway] [-t timeout] [-s source_addr] DESCRIPTION The Internet is a large and complex aggregation of network hardware, connected together by gateways. Tracking a single-point hardware or software failure can often be difficult. ping utilizes the ICMP protocol's mandatory ECHO request datagram to elicit an ICMP ECHOREPLY from a host or gateway. ECHO request datagrams (``pings'') have an IP and ICMP header, followed by a struct timeval, and then an arbitrary number of ``pad'' bytes used to fill out the packet. Default datagram length is 64 bytes (8 ICMP header bytes + 56 data bytes), but this may be changed using the command line option length. The number of ping packets is unlimited, unless an explicit count is specified. The default mode is to send a packet every timeout seconds and display the response, including sequence number and round-trip time if the packet size allows. Two other modes are available (which are mutually exclusive): SPECIAL MODES -c Use cisco style packet sending; that is, spew packets as fast as possible, but don't send packet N+1 until a reply or bounce or timeout has been registered for packet N. A '!' is printed for every valid response received and a '.' is printed when no packet is received during the timeout period. A duplicate response causes a '*' to be printed. When a ping request is bounced in transit, a '#' will be printed. -f Use floodping style packet sending; send packets as fast as possible, attempting to send at at least 100 packets per second. A '.' is printed for every packet sent and a backspaced '!' for every valid response (a backspaced '#' when a ping request is bounced in transit). The number of visible dots indicates how much ping is ``behind''. A '*' is printed whenever a duplicate packet is received. While waiting for outstanding packets during termination a '!' is printed per valid response and a '#' per bounced request. - 1 - Formatted: November 5, 2024 PING(8) PING(8) 990412 FLAGS -F Fast ping. In normal mode, send a packet as soon as a response is received without delaying for the regular timeout period. This is similar to cisco style except for the printing of the response messages. -Q Quick ping. This suppresses all normal output as well as the final statistics summary. The program quits with an ``alive'' indication as soon as a valid response is received. It quits with an ``unreachable'' indication as soon as a bounce message is received. -L Insert "loose source route" IP option in outgoing packets. Without explicit gateways given by the -g option, this selects a route to the destination host and back to the source host. This option only works on systems that allow setting of IP options. -R Insert "record route" IP option in outgoing packets, summarizing the routes the packets have traveled when the program quits. In "very verbose" mode, the route is displayed for each reply received. This option only works on systems that allow setting of IP options. -a All-address mode. If the destination host has multiple addresses, ping will probe all addresses if this option is set. Normally only the first address as returned by the DNS resolver is attempted. -m Missed mode. Enable printing of a summary of missed valid responses at the end. -n Numeric mode. Disable reverse hostname lookup of all IP addresses. By default both hostname and IP address of the destination host are displayed in the header, summary, and "record route" surveys, as well as in the response messages (the latter is safe since all lookups are now cached to avoid excessive nameserver queries). If the reverse hostname lookup fails, just the IP address is displayed. -q Quiet mode. Disable printing of ping response messages and special mode markers, only display the summary when quitting. This option is implied in quick (-Q) mode. -v Verbose mode. All received ICMP packets, including other than our own ECHOREPLY packets, are listed and a summary printout of their contents is made. When specified as -vv (very verbose), loose source route and record route information (if present) is displayed for each response received. -d Enable socket level debugging with the SO_DEBUG option. - 2 - Formatted: November 5, 2024 PING(8) PING(8) 990412 -r Enable socket level processing with the SO_DONTROUTE option. Bypass the normal routing tables and send directly to a host on an attached network. If the host is not on a directly-attached network, an error is returned. This option can be used to ping a local host through an interface that has no route through it (e.g., after the interface was dropped by routed(8C)). -V Just print the program version number, then exit. OPTIONS -t timeout In normal mode, this is the interval in seconds for sending ping messages. In cisco or fast mode, this is the timeout ping will wait for a reply before sending the next packet. In these modes a new ping is sent as soon as a valid reply is received. In flood mode this timeout does not apply. The default value is 1 second. -s source_addr Use the following IP address (which must be given as an IP number, not a hostname) as the source address in outgoing probe packets. On hosts with more than one IP address, this option can be used to force the source address to be something other than the IP address of the interface the probe packet is sent on. If the IP address is not one of this machine's interface addresses, an error is returned and nothing is sent. -g gateway Construct a "loose source route" via this gateway to the target host. Up to 8 of such intermediate hosts can be specified. This option only works on systems that allow setting of IP options. -l length Alternative option to specify the size of the ping packets. -k count Alternative option to limit the number of ping packets to be sent. -p preload Specifies the number of packets to preload. They are sent at startup before listening for a response. The default is to not send any preload packets. -b netbits Specify the number of bits in the netmask that applies to given addresses. This overrules the traditional class masks when checking whether a given address is a broadcast address. -D pattern Specifies the pattern to fill unused data in the packets. The default is to fill with the data position modulo 256. A pattern - 3 - Formatted: November 5, 2024 PING(8) PING(8) 990412 is a string of hex digit pairs used to specify the contents of the bytes of the packet. The pattern is replicated until it fills the entire packet. -T tos Set the type-of-service in probe packets to the given value (default zero). The value must be a decimal integer in the range 0 to 255. This option can be used to see if different types-of- service result in different delays. (If you are not running 4.4bsd, this may be academic since the normal network services like telnet and ftp don't let you control the TOS). Not all values of TOS are legal or meaningful - see the IP spec for definitions. Useful values are probably `-T 16' (low delay) and `-T 8' (high throughput). OPERATION When using ping for fault isolation, it should first be run on the local host, to verify that the local network interface is up and running. Then, hosts and gateways further and further away should be ``pinged''. ping sends one ECHO datagram per timeout period, and prints one line of output for every ECHOREPLY returned (or a warning if a bounce message is received or no response at all). If an optional length is specified, it is used as the length of the data portion of the ICMP ECHO request packet. The default length is 56 data bytes. If an optional count is given, only that number of requests is sent. Round-trip times and packet loss statistics are computed. When all responses have been received or the program times out (with a count specified), or if the program is terminated with a SIGINT, a brief summary is displayed. Additional info is printed depending on the command line flags. This program is intended for use in network testing, measurement and management. It should be used primarily for manual fault isolation. Because of the load it could impose on the network, it is unwise to use ping during normal operations or from automated scripts. EXIT STATUS ping returns a success (zero) exit code in case any valid response was received, and a failure (nonzero) code if there were none. WARNING Specifying both -L and -R simultaneously may not work in all circumstances, in the sense that it may confuse certain old Cisco routers. They will clobber their ARP cache, replacing the ethernet address of the client host with the ethernet address of the next hop along the route. This will make subsequent normal IP traffic to and from the client host impossible until the ARP cache is cleared again. This may take some time. Setting both options is restricted to the - 4 - Formatted: November 5, 2024 PING(8) PING(8) 990412 superuser, unless the program is compiled with a special compile switch indicating it is safe. BROADCAST ADDRESS Specifying the broadcast address of your local network as the target for ping yields a nice survey of all active hosts. The internal logic has been adapted to handle such broadcasts properly. All ping modes are supported, but a flood ping is restricted to the superuser only. Fast pings and cisco pings are now timeout-driven. Broadcasts to different networks usually don't cross gateways. Checking for a broadcast address is only rudimentary. The -b option may be necessary in case subnetting is employed. AUTHOR Mike Muuss CO-CONSPIRATORS Ron Natalie, David Paul Zimmerman, Jeffrey C Honig, Vernon Schryver Rewritten by Eric Wassenaar, Nikhef-H, <e07@nikhef.nl> SEE ALSO netstat(1), ifconfig(8), traceroute(8) - 5 - Formatted: November 5, 2024