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28 .\" @(#)ping.8 8.2 (Berkeley) 12/11/93
38 packets to network hosts
45 .Op Fl M Cm mask | time
50 .Op Fl s Ar packetsize
60 .Op Fl M Cm mask | time
65 .Op Fl s Ar packetsize
75 .No protocol Ap s mandatory
78 .Tn ICMP ECHO_RESPONSE
79 from a host or gateway.
87 and then an arbitrary number of
89 bytes used to fill out the packet.
90 The options are as follows:
91 .Bl -tag -width indent
97 character when no packet is received before the next packet
99 To cater for round-trip times that are longer than the interval
100 between transmissions, further missing packets cause a bell only
101 if the maximum number of unreceived packets has increased.
107 character in the output when any packet is received.
108 This option is ignored
109 if other format options are present.
116 If this option is not specified,
118 will operate until interrupted.
120 Set the Don't Fragment bit.
124 option on the socket being used.
127 Outputs packets as fast as they come back or one hundred times per second,
133 is printed, while for every
135 received a backspace is printed.
136 This provides a rapid display of how many packets are being dropped.
137 Only the super-user may use this option.
139 This can be very hard on a network and should be used with caution.
142 Source multicast packets with the given interface address.
143 This flag only applies if the ping destination is a multicast address.
148 .Em between sending each packet .
149 The default is to wait for one second between each packet.
150 The wait time may be fractional, but only the super-user may specify
151 values less than 1 second.
152 This option is incompatible with the
156 Suppress loopback of multicast packets.
157 This flag only applies if the ping destination is a multicast address.
163 sends that many packets as fast as possible before falling into its normal
165 Only the super-user may use this option.
166 .It Fl M Cm mask | time
175 print the netmask of the remote machine.
177 .Va net.inet.icmp.maskrepl
178 MIB variable to enable
182 print the origination, reception and transmission timestamps.
184 Set the IP Time To Live for outgoing packets.
185 If not specified, the kernel uses the value of the
190 No attempt will be made to lookup symbolic names for host addresses.
192 Exit successfully after receiving one reply packet.
195 specifies IPsec policy for the ping session.
196 For details please refer to
199 .Xr ipsec_set_policy 3 .
201 You may specify up to 16
203 bytes to fill out the packet you send.
204 This is useful for diagnosing data-dependent problems in a network.
207 will cause the sent packet to be filled with all
210 Somewhat quiet output.
212 display ICMP error messages that are in response to our query messages.
215 flag was required to display such errors, but
217 displays all ICMP error messages.
218 On a busy machine, this output can be overbearing.
223 prints out any ICMP error messages caused by its own ECHO_REQUEST
227 Nothing is displayed except the summary lines at startup time and
236 the route buffer on returned packets.
237 Note that the IP header is only large enough for nine such routes;
240 command is usually better at determining the route packets take to a
241 particular destination.
242 If more routes come back than should, such as due to an illegal spoofed
243 packet, ping will print the route list and then truncate it at the correct
245 Many hosts ignore or discard the
249 Bypass the normal routing tables and send directly to a host on an attached
251 If the host is not on a directly-attached network, an error is returned.
252 This option can be used to ping a local host through an interface
253 that has no route through it
254 (e.g., after the interface was dropped by
257 Use the following IP address as the source address in outgoing packets.
258 On hosts with more than one IP address, this option can be used to
259 force the source address to be something other than the IP address
260 of the interface the probe packet is sent on.
262 is not one of this machine's interface addresses, an error is
263 returned and nothing is sent.
264 .It Fl s Ar packetsize
265 Specify the number of data bytes to be sent.
266 The default is 56, which translates into 64
268 data bytes when combined
272 Only the super-user may specify values more than default.
274 Set the IP Time To Live for multicasted packets.
275 This flag only applies if the ping destination is a multicast address.
277 Specify a timeout, in seconds, before ping exits regardless of how
278 many packets have been received.
284 that are received are listed.
286 Use the specified type of service.
291 for fault isolation, it should first be run on the local host, to verify
292 that the local network interface is up and running.
293 Then, hosts and gateways further and further away should be
295 Round-trip times and packet loss statistics are computed.
296 If duplicate packets are received, they are not included in the packet
297 loss calculation, although the round trip time of these packets is used
298 in calculating the round-trip time statistics.
299 When the specified number of packets have been sent
301 or if the program is terminated with a
303 a brief summary is displayed, showing the number of packets sent and
304 received, and the minimum, mean, maximum, and standard deviation of
305 the round-trip times.
315 signal, the current number of packets sent and received, and the
316 minimum, mean, and maximum of the round-trip times will be written to
317 the standard error output.
319 This program is intended for use in network testing, measurement and
321 Because of the load it can impose on the network, it is unwise to use
323 during normal operations or from automated scripts.
324 .Sh ICMP PACKET DETAILS
325 An IP header without options is 20 bytes.
329 packet contains an additional 8 bytes worth of
331 header followed by an arbitrary amount of data.
334 is given, this indicated the size of this extra piece of data
336 Thus the amount of data received inside of an IP packet of type
339 will always be 8 bytes more than the requested data space
344 If the data space is at least eight bytes large,
346 uses the first eight bytes of this space to include a timestamp which
347 it uses in the computation of round trip times.
348 If less than eight bytes of pad are specified, no round trip times are
350 .Sh DUPLICATE AND DAMAGED PACKETS
353 utility will report duplicate and damaged packets.
354 Duplicate packets should never occur when pinging a unicast address,
355 and seem to be caused by
356 inappropriate link-level retransmissions.
357 Duplicates may occur in many situations and are rarely
359 a good sign, although the presence of low levels of duplicates may not
360 always be cause for alarm.
361 Duplicates are expected when pinging a broadcast or multicast address,
362 since they are not really duplicates but replies from different hosts
365 Damaged packets are obviously serious cause for alarm and often
366 indicate broken hardware somewhere in the
368 packet's path (in the network or in the hosts).
369 .Sh TRYING DIFFERENT DATA PATTERNS
372 layer should never treat packets differently depending on the data
373 contained in the data portion.
374 Unfortunately, data-dependent problems have been known to sneak into
375 networks and remain undetected for long periods of time.
376 In many cases the particular pattern that will have problems is something
377 that does not have sufficient
379 such as all ones or all zeros, or a pattern right at the edge, such as
382 necessarily enough to specify a data pattern of all zeros (for example)
383 on the command line because the pattern that is of interest is
384 at the data link level, and the relationship between what you type and
385 what the controllers transmit can be complicated.
387 This means that if you have a data-dependent problem you will probably
388 have to do a lot of testing to find it.
389 If you are lucky, you may manage to find a file that either
391 be sent across your network or that takes much longer to transfer than
392 other similar length files.
393 You can then examine this file for repeated patterns that you can test
401 value of an IP packet represents the maximum number of IP routers
402 that the packet can go through before being thrown away.
403 In current practice you can expect each router in the Internet to decrement
406 field by exactly one.
410 specification recommends setting the
414 packets to 64, but many systems use smaller values
420 The maximum possible value of this field is 255, and most
426 .Tn ICMP ECHO_REQUEST
428 This is why you will find you can
430 some hosts, but not reach them with
437 prints the ttl value from the packet it receives.
438 When a remote system receives a ping packet, it can do one of three things
441 field in its response:
444 Not change it; this is what
446 systems did before the
451 value in the received packet will be 255 minus the
452 number of routers in the round-trip path.
454 Set it to 255; this is what current
459 value in the received packet will be 255 minus the
460 number of routers in the path
468 Set it to some other value.
469 Some machines use the same value for
471 packets that they use for
473 packets, for example either 30 or 60.
474 Others may use completely wild values.
479 utility returns an exit status of zero if at least one response was
480 heard from the specified
482 a status of two if the transmission was successful but no responses
483 were received; or another value
486 if an error occurred.
500 utility was written by
502 while at the US Army Ballistics
505 Many Hosts and Gateways ignore the
509 The maximum IP header length is too small for options like
511 to be completely useful.
513 not much that can be done about this, however.
515 Flood pinging is not recommended in general, and flood pinging the
516 broadcast address should only be done under very controlled conditions.
520 option is not worth much on busy hosts.