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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 $
38 packets to network hosts
43 .Op Fl G Ar sweepmaxsize
44 .Op Fl g Ar sweepminsize
45 .Op Fl h Ar sweepincrsize
48 .Op Fl M Cm mask | time
52 .Op Fl s Ar packetsize
63 .Op Fl M Cm mask | time
67 .Op Fl s Ar packetsize
78 .No protocol Ap s mandatory
81 .Tn ICMP ECHO_RESPONSE
82 from a host or gateway.
90 and then an arbitrary number of
92 bytes used to fill out the packet.
93 The options are as follows:
94 .Bl -tag -width indent
100 character when no packet is received before the next packet
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.
110 character in the output when any packet is received.
111 This option is ignored
112 if other format options are present.
119 If this option is not specified,
121 will operate until interrupted.
122 If this option is specified in conjunction with ping sweeps,
123 each sweep will consist of
127 Set the Don't Fragment bit.
131 option on the socket being used.
134 Outputs packets as fast as they come back or one hundred times per second,
140 is printed, while for every
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.
146 This can be very hard on a network and should be used with caution.
148 .It Fl G Ar sweepmaxsize
149 Specify the maximum size of
151 payload when sending sweeping pings.
152 This option is required for ping sweeps.
153 .It Fl g Ar sweepminsize
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
162 each sweep when sending sweeping pings.
163 The default value is 1.
165 Source multicast packets with the given interface address.
166 This flag only applies if the ping destination is a multicast address.
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
179 Suppress loopback of multicast packets.
180 This flag only applies if the ping destination is a multicast address.
186 sends that many packets as fast as possible before falling into its normal
188 Only the super-user may use this option.
189 .It Fl M Cm mask | time
198 print the netmask of the remote machine.
200 .Va net.inet.icmp.maskrepl
201 MIB variable to enable
205 print the origination, reception and transmission timestamps.
207 Set the IP Time To Live for outgoing packets.
208 If not specified, the kernel uses the value of the
213 No attempt will be made to lookup symbolic names for host addresses.
215 Exit successfully after receiving one reply packet.
217 You may specify up to 16
219 bytes to fill out the packet you send.
220 This is useful for diagnosing data-dependent problems in a network.
223 will cause the sent packet to be filled with all
226 Somewhat quiet output.
228 display ICMP error messages that are in response to our query messages.
231 flag was required to display such errors, but
233 displays all ICMP error messages.
234 On a busy machine, this output can be overbearing.
239 prints out any ICMP error messages caused by its own ECHO_REQUEST
243 Nothing is displayed except the summary lines at startup time and
252 the route buffer on returned packets.
253 Note that the IP header is only large enough for nine such routes;
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
261 Many hosts ignore or discard the
265 Bypass the normal routing tables and send directly to a host on an attached
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
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.
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
284 data bytes when combined
288 This option cannot be used with ping sweeps.
290 Set the IP Time To Live for multicasted packets.
291 This flag only applies if the ping destination is a multicast address.
293 Specify a timeout, in seconds, before ping exits regardless of how
294 many packets have been received.
300 that are received are listed.
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.
306 Use the specified type of service.
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
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
321 or if the program is terminated with a
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.
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.
339 This program is intended for use in network testing, measurement and
341 Because of the load it can impose on the network, it is unwise to use
343 during normal operations or from automated scripts.
344 .Sh ICMP PACKET DETAILS
345 An IP header without options is 20 bytes.
349 packet contains an additional 8 bytes worth of
351 header followed by an arbitrary amount of data.
354 is given, this indicated the size of this extra piece of data
356 Thus the amount of data received inside of an IP packet of type
359 will always be 8 bytes more than the requested data space
364 If the data space is at least eight bytes large,
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
370 .Sh DUPLICATE AND DAMAGED PACKETS
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
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
385 Damaged packets are obviously serious cause for alarm and often
386 indicate broken hardware somewhere in the
388 packet's path (in the network or in the hosts).
389 .Sh TRYING DIFFERENT DATA PATTERNS
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
399 such as all ones or all zeros, or a pattern right at the edge, such as
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.
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
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
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
426 field by exactly one.
430 specification recommends setting the
434 packets to 64, but many systems use smaller values
440 The maximum possible value of this field is 255, and most
446 .Tn ICMP ECHO_REQUEST
448 This is why you will find you can
450 some hosts, but not reach them with
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
461 field in its response:
464 Not change it; this is what
466 systems did before the
471 value in the received packet will be 255 minus the
472 number of routers in the round-trip path.
474 Set it to 255; this is what current
479 value in the received packet will be 255 minus the
480 number of routers in the path
488 Set it to some other value.
489 Some machines use the same value for
491 packets that they use for
493 packets, for example either 30 or 60.
494 Others may use completely wild values.
499 utility returns an exit status of zero if at least one response was
500 heard from the specified
502 a status of two if the transmission was successful but no responses
503 were received; or another value
506 if an error occurred.
522 utility was written by
524 while at the US Army Ballistics
527 Many Hosts and Gateways ignore the
531 The maximum IP header length is too small for options like
533 to be completely useful.
535 not much that can be done about this, however.
537 Flood pinging is not recommended in general, and flood pinging the
538 broadcast address should only be done under very controlled conditions.
542 option is not worth much on busy hosts.