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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 .\" $DragonFly: src/sbin/ping/ping.8,v 1.5 2007/05/29 10:21:41 hasso Exp $
39 packets to network hosts
44 .Op Fl G Ar sweepmaxsize
45 .Op Fl g Ar sweepminsize
46 .Op Fl h Ar sweepincrsize
49 .Op Fl M Cm mask | time
54 .Op Fl s Ar packetsize
65 .Op Fl M Cm mask | time
70 .Op Fl s Ar packetsize
81 .No protocol Ap s mandatory
84 .Tn ICMP ECHO_RESPONSE
85 from a host or gateway.
93 and then an arbitrary number of
95 bytes used to fill out the packet.
96 The options are as follows:
97 .Bl -tag -width indent
103 character when no packet is received before the next packet
105 To cater for round-trip times that are longer than the interval
106 between transmissions, further missing packets cause a bell only
107 if the maximum number of unreceived packets has increased.
113 character in the output when any packet is received.
114 This option is ignored
115 if other format options are present.
122 If this option is not specified,
124 will operate until interrupted.
125 If this option is specified in conjunction with ping sweeps,
126 each sweep will consist of
130 Set the Don't Fragment bit.
134 option on the socket being used.
137 Outputs packets as fast as they come back or one hundred times per second,
143 is printed, while for every
145 received a backspace is printed.
146 This provides a rapid display of how many packets are being dropped.
147 Only the super-user may use this option.
149 This can be very hard on a network and should be used with caution.
151 .It Fl G Ar sweepmaxsize
152 Specify the maximum size of
154 payload when sending sweeping pings.
155 This option is required for ping sweeps.
156 .It Fl g Ar sweepminsize
159 payload to start with when sending sweeping pings.
160 The default value is 0.
161 .It Fl h Ar sweepincrsize
162 Specify the number of bytes to increment the size of
165 each sweep when sending sweeping pings.
166 The default value is 1.
168 Source multicast packets with the given interface address.
169 This flag only applies if the ping destination is a multicast address.
174 .Em between sending each packet .
175 The default is to wait for one second between each packet.
176 The wait time may be fractional, but only the super-user may specify
177 values less than 1 second.
178 This option is incompatible with the
182 Suppress loopback of multicast packets.
183 This flag only applies if the ping destination is a multicast address.
189 sends that many packets as fast as possible before falling into its normal
191 Only the super-user may use this option.
192 .It Fl M Cm mask | time
201 print the netmask of the remote machine.
203 .Va net.inet.icmp.maskrepl
204 MIB variable to enable
208 print the origination, reception and transmission timestamps.
210 Set the IP Time To Live for outgoing packets.
211 If not specified, the kernel uses the value of the
216 No attempt will be made to lookup symbolic names for host addresses.
218 Exit successfully after receiving one reply packet.
221 specifies IPsec policy for the ping session.
222 For details please refer to
225 .Xr ipsec_set_policy 3 .
227 You may specify up to 16
229 bytes to fill out the packet you send.
230 This is useful for diagnosing data-dependent problems in a network.
233 will cause the sent packet to be filled with all
236 Somewhat quiet output.
238 display ICMP error messages that are in response to our query messages.
241 flag was required to display such errors, but
243 displays all ICMP error messages.
244 On a busy machine, this output can be overbearing.
249 prints out any ICMP error messages caused by its own ECHO_REQUEST
253 Nothing is displayed except the summary lines at startup time and
262 the route buffer on returned packets.
263 Note that the IP header is only large enough for nine such routes;
266 command is usually better at determining the route packets take to a
267 particular destination.
268 If more routes come back than should, such as due to an illegal spoofed
269 packet, ping will print the route list and then truncate it at the correct
271 Many hosts ignore or discard the
275 Bypass the normal routing tables and send directly to a host on an attached
277 If the host is not on a directly-attached network, an error is returned.
278 This option can be used to ping a local host through an interface
279 that has no route through it
280 (e.g., after the interface was dropped by
283 Use the following IP address as the source address in outgoing packets.
284 On hosts with more than one IP address, this option can be used to
285 force the source address to be something other than the IP address
286 of the interface the probe packet is sent on.
288 is not one of this machine's interface addresses, an error is
289 returned and nothing is sent.
290 .It Fl s Ar packetsize
291 Specify the number of data bytes to be sent.
292 The default is 56, which translates into 64
294 data bytes when combined
298 Only the super-user may specify values more than default.
299 This option cannot be used with ping sweeps.
301 Set the IP Time To Live for multicasted packets.
302 This flag only applies if the ping destination is a multicast address.
304 Specify a timeout, in seconds, before ping exits regardless of how
305 many packets have been received.
311 that are received are listed.
313 Time in milliseconds to wait for a reply for each packet sent.
314 If a reply arrives later, the packet is not printed as replied, but
315 considered as replied when calculating statistics.
317 Use the specified type of service.
322 for fault isolation, it should first be run on the local host, to verify
323 that the local network interface is up and running.
324 Then, hosts and gateways further and further away should be
326 Round-trip times and packet loss statistics are computed.
327 If duplicate packets are received, they are not included in the packet
328 loss calculation, although the round trip time of these packets is used
329 in calculating the round-trip time statistics.
330 When the specified number of packets have been sent
332 or if the program is terminated with a
334 a brief summary is displayed, showing the number of packets sent and
335 received, and the minimum, mean, maximum, and standard deviation of
336 the round-trip times.
346 signal, the current number of packets sent and received, and the
347 minimum, mean, and maximum of the round-trip times will be written to
348 the standard error output.
350 This program is intended for use in network testing, measurement and
352 Because of the load it can impose on the network, it is unwise to use
354 during normal operations or from automated scripts.
355 .Sh ICMP PACKET DETAILS
356 An IP header without options is 20 bytes.
360 packet contains an additional 8 bytes worth of
362 header followed by an arbitrary amount of data.
365 is given, this indicated the size of this extra piece of data
367 Thus the amount of data received inside of an IP packet of type
370 will always be 8 bytes more than the requested data space
375 If the data space is at least eight bytes large,
377 uses the first eight bytes of this space to include a timestamp which
378 it uses in the computation of round trip times.
379 If less than eight bytes of pad are specified, no round trip times are
381 .Sh DUPLICATE AND DAMAGED PACKETS
384 utility will report duplicate and damaged packets.
385 Duplicate packets should never occur when pinging a unicast address,
386 and seem to be caused by
387 inappropriate link-level retransmissions.
388 Duplicates may occur in many situations and are rarely
390 a good sign, although the presence of low levels of duplicates may not
391 always be cause for alarm.
392 Duplicates are expected when pinging a broadcast or multicast address,
393 since they are not really duplicates but replies from different hosts
396 Damaged packets are obviously serious cause for alarm and often
397 indicate broken hardware somewhere in the
399 packet's path (in the network or in the hosts).
400 .Sh TRYING DIFFERENT DATA PATTERNS
403 layer should never treat packets differently depending on the data
404 contained in the data portion.
405 Unfortunately, data-dependent problems have been known to sneak into
406 networks and remain undetected for long periods of time.
407 In many cases the particular pattern that will have problems is something
408 that does not have sufficient
410 such as all ones or all zeros, or a pattern right at the edge, such as
413 necessarily enough to specify a data pattern of all zeros (for example)
414 on the command line because the pattern that is of interest is
415 at the data link level, and the relationship between what you type and
416 what the controllers transmit can be complicated.
418 This means that if you have a data-dependent problem you will probably
419 have to do a lot of testing to find it.
420 If you are lucky, you may manage to find a file that either
422 be sent across your network or that takes much longer to transfer than
423 other similar length files.
424 You can then examine this file for repeated patterns that you can test
432 value of an IP packet represents the maximum number of IP routers
433 that the packet can go through before being thrown away.
434 In current practice you can expect each router in the Internet to decrement
437 field by exactly one.
441 specification recommends setting the
445 packets to 64, but many systems use smaller values
451 The maximum possible value of this field is 255, and most
457 .Tn ICMP ECHO_REQUEST
459 This is why you will find you can
461 some hosts, but not reach them with
468 prints the ttl value from the packet it receives.
469 When a remote system receives a ping packet, it can do one of three things
472 field in its response:
475 Not change it; this is what
477 systems did before the
482 value in the received packet will be 255 minus the
483 number of routers in the round-trip path.
485 Set it to 255; this is what current
490 value in the received packet will be 255 minus the
491 number of routers in the path
499 Set it to some other value.
500 Some machines use the same value for
502 packets that they use for
504 packets, for example either 30 or 60.
505 Others may use completely wild values.
510 utility returns an exit status of zero if at least one response was
511 heard from the specified
513 a status of two if the transmission was successful but no responses
514 were received; or another value
517 if an error occurred.
531 utility was written by
533 while at the US Army Ballistics
536 Many Hosts and Gateways ignore the
540 The maximum IP header length is too small for options like
542 to be completely useful.
544 not much that can be done about this, however.
546 Flood pinging is not recommended in general, and flood pinging the
547 broadcast address should only be done under very controlled conditions.
551 option is not worth much on busy hosts.
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