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28 .\" @(#)ping.8 8.2 (Berkeley) 12/11/93
29 .\" $FreeBSD: src/sbin/ping/ping.8,v 1.54 2006/04/05 12:30:42 glebius Exp $
30 .\"
31 .Dd March 4, 2024
32 .Dt PING 8
33 .Os
34 .Sh NAME
35 .Nm ping
36 .Nd send
37 .Tn ICMP ECHO_REQUEST
38 packets to network hosts
39 .Sh SYNOPSIS
40 .Nm
41 .Op Fl AaDdfnoQqRrv
42 .Op Fl c Ar count
43 .Op Fl G Ar sweepmaxsize
44 .Op Fl g Ar sweepminsize
45 .Op Fl h Ar sweepincrsize
46 .Op Fl i Ar wait
47 .Op Fl l Ar preload
48 .Op Fl M Cm mask | time
49 .Op Fl m Ar ttl
50 .Op Fl p Ar pattern
51 .Op Fl S Ar src_addr
52 .Op Fl s Ar packetsize
53 .Op Fl t Ar timeout
54 .Op Fl W Ar waittime
55 .Op Fl z Ar tos
56 .Ar host
57 .Nm
58 .Op Fl AaDdfLnoQqRrv
59 .Op Fl c Ar count
60 .Op Fl I Ar iface
61 .Op Fl i Ar wait
62 .Op Fl l Ar preload
63 .Op Fl M Cm mask | time
64 .Op Fl m Ar ttl
65 .Op Fl p Ar pattern
66 .Op Fl S Ar src_addr
67 .Op Fl s Ar packetsize
68 .Op Fl T Ar ttl
69 .Op Fl t Ar timeout
70 .Op Fl W Ar waittime
71 .Op Fl z Ar tos
72 .Ar mcast-group
73 .Sh DESCRIPTION
74 The
75 .Nm
76 utility uses the
77 .Tn ICMP
78 .No protocol Ap s mandatory
79 .Tn ECHO_REQUEST
80 datagram to elicit an
81 .Tn ICMP ECHO_RESPONSE
82 from a host or gateway.
83 .Tn ECHO_REQUEST
84 datagrams
85 .Pq Dq pings
86 have an IP and
87 .Tn ICMP
88 header, followed by a
89 .Dq struct timeval
90 and then an arbitrary number of
91 .Dq pad
92 bytes used to fill out the packet.
93 The options are as follows:
94 .Bl -tag -width indent
95 .It Fl A
96 Audible.
97 Output a bell
98 .Tn ( ASCII
99 0x07)
100 character when no packet is received before the next packet
101 is transmitted.
102 To cater for round-trip times that are longer than the interval
103 between transmissions, further missing packets cause a bell only
104 if the maximum number of unreceived packets has increased.
105 .It Fl a
106 Audible.
107 Include a bell
108 .Tn ( ASCII
109 0x07)
110 character in the output when any packet is received.
111 This option is ignored
112 if other format options are present.
113 .It Fl c Ar count
114 Stop after sending
115 (and receiving)
116 .Ar count
117 .Tn ECHO_RESPONSE
118 packets.
119 If this option is not specified,
120 .Nm
121 will operate until interrupted.
122 If this option is specified in conjunction with ping sweeps,
123 each sweep will consist of
124 .Ar count
125 packets.
126 .It Fl D
127 Set the Don't Fragment bit.
128 .It Fl d
129 Set the
130 .Dv SO_DEBUG
131 option on the socket being used.
132 .It Fl f
133 Flood ping.
134 Outputs packets as fast as they come back or one hundred times per second,
135 whichever is more.
136 For every
137 .Tn ECHO_REQUEST
138 sent a period
139 .Dq .\&
140 is printed, while for every
141 .Tn ECHO_REPLY
142 received a backspace is printed.
143 This provides a rapid display of how many packets are being dropped.
144 Only the super-user may use this option.
145 .Bf -emphasis
146 This can be very hard on a network and should be used with caution.
147 .Ef
148 .It Fl G Ar sweepmaxsize
149 Specify the maximum size of
150 .Tn ICMP
151 payload when sending sweeping pings.
152 This option is required for ping sweeps.
153 .It Fl g Ar sweepminsize
154 Specify the size of
155 .Tn ICMP
156 payload to start with when sending sweeping pings.
157 The default value is 0.
158 .It Fl h Ar sweepincrsize
159 Specify the number of bytes to increment the size of
160 .Tn ICMP
161 payload after
162 each sweep when sending sweeping pings.
163 The default value is 1.
164 .It Fl I Ar iface
165 Source multicast packets with the given interface address.
166 This flag only applies if the ping destination is a multicast address.
167 .It Fl i Ar wait
168 Wait
169 .Ar wait
170 seconds
171 .Em between sending each packet .
172 The default is to wait for one second between each packet.
173 Only the super-user may specify values less than 0.002 second
174 (i.e., 2 milliseconds).
175 This option is incompatible with the
176 .Fl f
177 option.
178 .It Fl L
179 Suppress loopback of multicast packets.
180 This flag only applies if the ping destination is a multicast address.
181 .It Fl l Ar preload
182 If
183 .Ar preload
184 is specified,
185 .Nm
186 sends that many packets as fast as possible before falling into its normal
187 mode of behavior.
188 Only the super-user may use this option.
189 .It Fl M Cm mask | time
190 Use
191 .Dv ICMP_MASKREQ
192 or
193 .Dv ICMP_TSTAMP
194 instead of
195 .Dv ICMP_ECHO .
196 For
197 .Cm mask ,
198 print the netmask of the remote machine.
199 Set the
200 .Va net.inet.icmp.maskrepl
201 MIB variable to enable
202 .Dv ICMP_MASKREPLY .
203 For
204 .Cm time ,
205 print the origination, reception and transmission timestamps.
206 .It Fl m Ar ttl
207 Set the IP Time To Live for outgoing packets.
208 If not specified, the kernel uses the value of the
209 .Va net.inet.ip.ttl
210 MIB variable.
211 .It Fl n
212 Numeric output only.
213 No attempt will be made to lookup symbolic names for host addresses.
214 .It Fl o
215 Exit successfully after receiving one reply packet.
216 .It Fl p Ar pattern
217 You may specify up to 16
218 .Dq pad
219 bytes to fill out the packet you send.
220 This is useful for diagnosing data-dependent problems in a network.
221 For example,
222 .Dq Li \-p ff
223 will cause the sent packet to be filled with all
224 ones.
225 .It Fl Q
226 Somewhat quiet output.
227 .No Don Ap t
228 display ICMP error messages that are in response to our query messages.
229 Originally, the
230 .Fl v
231 flag was required to display such errors, but
232 .Fl v
233 displays all ICMP error messages.
234 On a busy machine, this output can be overbearing.
235 Without the
236 .Fl Q
237 flag,
238 .Nm
239 prints out any ICMP error messages caused by its own ECHO_REQUEST
240 messages.
241 .It Fl q
242 Quiet output.
243 Nothing is displayed except the summary lines at startup time and
244 when finished.
245 .It Fl R
246 Record route.
247 Includes the
248 .Tn RECORD_ROUTE
249 option in the
250 .Tn ECHO_REQUEST
251 packet and displays
252 the route buffer on returned packets.
253 Note that the IP header is only large enough for nine such routes;
254 the
255 .Xr traceroute 8
256 command is usually better at determining the route packets take to a
257 particular destination.
258 If more routes come back than should, such as due to an illegal spoofed
259 packet, ping will print the route list and then truncate it at the correct
260 spot.
261 Many hosts ignore or discard the
262 .Tn RECORD_ROUTE
263 option.
264 .It Fl r
265 Bypass the normal routing tables and send directly to a host on an attached
266 network.
267 If the host is not on a directly-attached network, an error is returned.
268 This option can be used to ping a local host through an interface
269 that has no route through it
270 (e.g., after the interface was dropped by
271 .Xr routed 8 ) .
272 .It Fl S Ar src_addr
273 Use the following IP address as the source address in outgoing packets.
274 On hosts with more than one IP address, this option can be used to
275 force the source address to be something other than the IP address
276 of the interface the probe packet is sent on.
277 If the IP address
278 is not one of this machine's interface addresses, an error is
279 returned and nothing is sent.
280 .It Fl s Ar packetsize
281 Specify the number of data bytes to be sent.
282 The default is 56, which translates into 64
283 .Tn ICMP
284 data bytes when combined
285 with the 8 bytes of
286 .Tn ICMP
287 header data.
288 This option cannot be used with ping sweeps.
289 .It Fl T Ar ttl
290 Set the IP Time To Live for multicasted packets.
291 This flag only applies if the ping destination is a multicast address.
292 .It Fl t Ar timeout
293 Specify a timeout, in seconds, before ping exits regardless of how
294 many packets have been received.
295 .It Fl v
296 Verbose output.
297 .Tn ICMP
298 packets other than
299 .Tn ECHO_RESPONSE
300 that are received are listed.
301 .It Fl W Ar waittime
302 Time in milliseconds to wait for a reply for each packet sent.
303 If a reply arrives later, the packet is not printed as replied, but
304 considered as replied when calculating statistics.
305 .It Fl z Ar tos
306 Use the specified type of service.
307 .El
308 .Pp
309 When using
310 .Nm
311 for fault isolation, it should first be run on the local host, to verify
312 that the local network interface is up and running.
313 Then, hosts and gateways further and further away should be
314 .Dq pinged .
315 Round-trip times and packet loss statistics are computed.
316 If duplicate packets are received, they are not included in the packet
317 loss calculation, although the round trip time of these packets is used
318 in calculating the round-trip time statistics.
319 When the specified number of packets have been sent
320 (and received)
321 or if the program is terminated with a
322 .Dv SIGINT ,
323 a brief summary is displayed, showing the number of packets sent and
324 received, and the minimum, mean, maximum, and standard deviation of
325 the round-trip times.
326 .Pp
327 If
328 .Nm
329 receives a
330 .Dv SIGINFO
331 (see the
332 .Cm status
333 argument for
334 .Xr stty 1 )
335 signal, the current number of packets sent and received, and the
336 minimum, mean, and maximum of the round-trip times will be written to
337 the standard error output.
338 .Pp
339 This program is intended for use in network testing, measurement and
340 management.
341 Because of the load it can impose on the network, it is unwise to use
342 .Nm
343 during normal operations or from automated scripts.
344 .Sh ICMP PACKET DETAILS
345 An IP header without options is 20 bytes.
346 An
347 .Tn ICMP
348 .Tn ECHO_REQUEST
349 packet contains an additional 8 bytes worth of
350 .Tn ICMP
351 header followed by an arbitrary amount of data.
352 When a
353 .Ar packetsize
354 is given, this indicated the size of this extra piece of data
355 (the default is 56).
356 Thus the amount of data received inside of an IP packet of type
357 .Tn ICMP
358 .Tn ECHO_REPLY
359 will always be 8 bytes more than the requested data space
360 (the
361 .Tn ICMP
362 header).
363 .Pp
364 If the data space is at least eight bytes large,
365 .Nm
366 uses the first eight bytes of this space to include a timestamp which
367 it uses in the computation of round trip times.
368 If less than eight bytes of pad are specified, no round trip times are
369 given.
370 .Sh DUPLICATE AND DAMAGED PACKETS
371 The
372 .Nm
373 utility will report duplicate and damaged packets.
374 Duplicate packets should never occur when pinging a unicast address,
375 and seem to be caused by
376 inappropriate link-level retransmissions.
377 Duplicates may occur in many situations and are rarely
378 (if ever)
379 a good sign, although the presence of low levels of duplicates may not
380 always be cause for alarm.
381 Duplicates are expected when pinging a broadcast or multicast address,
382 since they are not really duplicates but replies from different hosts
383 to the same request.
384 .Pp
385 Damaged packets are obviously serious cause for alarm and often
386 indicate broken hardware somewhere in the
387 .Nm
388 packet's path (in the network or in the hosts).
389 .Sh TRYING DIFFERENT DATA PATTERNS
390 The
391 (inter)network
392 layer should never treat packets differently depending on the data
393 contained in the data portion.
394 Unfortunately, data-dependent problems have been known to sneak into
395 networks and remain undetected for long periods of time.
396 In many cases the particular pattern that will have problems is something
397 that does not have sufficient
398 .Dq transitions ,
399 such as all ones or all zeros, or a pattern right at the edge, such as
400 almost all zeros.
401 It is not
402 necessarily enough to specify a data pattern of all zeros (for example)
403 on the command line because the pattern that is of interest is
404 at the data link level, and the relationship between what you type and
405 what the controllers transmit can be complicated.
406 .Pp
407 This means that if you have a data-dependent problem you will probably
408 have to do a lot of testing to find it.
409 If you are lucky, you may manage to find a file that either
410 cannot
411 be sent across your network or that takes much longer to transfer than
412 other similar length files.
413 You can then examine this file for repeated patterns that you can test
414 using the
415 .Fl p
416 option of
417 .Nm .
418 .Sh TTL DETAILS
419 The
420 .Tn TTL
421 value of an IP packet represents the maximum number of IP routers
422 that the packet can go through before being thrown away.
423 In current practice you can expect each router in the Internet to decrement
424 the
425 .Tn TTL
426 field by exactly one.
427 .Pp
428 The
429 .Tn TCP/IP
430 specification recommends setting the
431 .Tn TTL
432 field for
433 .Tn IP
434 packets to 64, but many systems use smaller values
435 .No ( Bx 4.3
436 uses 30,
437 .Bx 4.2
438 used 15).
439 .Pp
440 The maximum possible value of this field is 255, and most
441 .Ux
442 systems set
443 the
444 .Tn TTL
445 field of
446 .Tn ICMP ECHO_REQUEST
447 packets to 255.
448 This is why you will find you can
449 .Dq ping
450 some hosts, but not reach them with
451 .Xr telnet 1
452 or
453 .Xr ftp 1 .
454 .Pp
455 In normal operation
456 .Nm
457 prints the ttl value from the packet it receives.
458 When a remote system receives a ping packet, it can do one of three things
459 with the
460 .Tn TTL
461 field in its response:
462 .Bl -bullet
463 .It
464 Not change it; this is what
465 .Bx
466 systems did before the
467 .Bx 4.3 tahoe
468 release.
469 In this case the
470 .Tn TTL
471 value in the received packet will be 255 minus the
472 number of routers in the round-trip path.
473 .It
474 Set it to 255; this is what current
475 .Bx
476 systems do.
477 In this case the
478 .Tn TTL
479 value in the received packet will be 255 minus the
480 number of routers in the path
481 .Em from
482 the remote system
483 .Em to
484 the
485 .Nm Ns Em ing
486 host.
487 .It
488 Set it to some other value.
489 Some machines use the same value for
490 .Tn ICMP
491 packets that they use for
492 .Tn TCP
493 packets, for example either 30 or 60.
494 Others may use completely wild values.
495 .El
496 .Sh EXIT STATUS
497 The
498 .Nm
499 utility returns an exit status of zero if at least one response was
500 heard from the specified
501 .Ar host ;
502 a status of two if the transmission was successful but no responses
503 were received; or another value
504 (from
505 .In sysexits.h )
506 if an error occurred.
507 .Sh SEE ALSO
508 .Xr netstat 1 ,
509 .Xr ifconfig 8 ,
510 .Xr ping6 8 ,
511 .Xr routed 8 ,
512 .Xr traceroute 8 ,
513 .Xr traceroute6 8
514 .Sh HISTORY
515 The
516 .Nm
517 utility appeared in
518 .Bx 4.3 .
519 .Sh AUTHORS
520 The original
521 .Nm
522 utility was written by
523 .An Mike Muuss
524 while at the US Army Ballistics
525 Research Laboratory.
526 .Sh BUGS
527 Many Hosts and Gateways ignore the
528 .Tn RECORD_ROUTE
529 option.
530 .Pp
531 The maximum IP header length is too small for options like
532 .Tn RECORD_ROUTE
533 to be completely useful.
534 .No There Ap s
535 not much that can be done about this, however.
536 .Pp
537 Flood pinging is not recommended in general, and flood pinging the
538 broadcast address should only be done under very controlled conditions.
539 .Pp
540 The
541 .Fl v
542 option is not worth much on busy hosts.