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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
53 .Op Fl s Ar packetsize
64 .Op Fl M Cm mask | time
69 .Op Fl s Ar packetsize
80 .No protocol Ap s mandatory
83 .Tn ICMP ECHO_RESPONSE
84 from a host or gateway.
92 and then an arbitrary number of
94 bytes used to fill out the packet.
95 The options are as follows:
96 .Bl -tag -width indent
102 character when no packet is received before the next packet
104 To cater for round-trip times that are longer than the interval
105 between transmissions, further missing packets cause a bell only
106 if the maximum number of unreceived packets has increased.
112 character in the output when any packet is received.
113 This option is ignored
114 if other format options are present.
121 If this option is not specified,
123 will operate until interrupted.
124 If this option is specified in conjunction with ping sweeps,
125 each sweep will consist of
129 Set the Don't Fragment bit.
133 option on the socket being used.
136 Outputs packets as fast as they come back or one hundred times per second,
142 is printed, while for every
144 received a backspace is printed.
145 This provides a rapid display of how many packets are being dropped.
146 Only the super-user may use this option.
148 This can be very hard on a network and should be used with caution.
150 .It Fl G Ar sweepmaxsize
151 Specify the maximum size of
153 payload when sending sweeping pings.
154 This option is required for ping sweeps.
155 .It Fl g Ar sweepminsize
158 payload to start with when sending sweeping pings.
159 The default value is 0.
160 .It Fl h Ar sweepincrsize
161 Specify the number of bytes to increment the size of
164 each sweep when sending sweeping pings.
165 The default value is 1.
167 Source multicast packets with the given interface address.
168 This flag only applies if the ping destination is a multicast address.
173 .Em between sending each packet .
174 The default is to wait for one second between each packet.
175 The wait time may be fractional, but only the super-user may specify
176 values less than 1 second.
177 This option is incompatible with the
181 Suppress loopback of multicast packets.
182 This flag only applies if the ping destination is a multicast address.
188 sends that many packets as fast as possible before falling into its normal
190 Only the super-user may use this option.
191 .It Fl M Cm mask | time
200 print the netmask of the remote machine.
202 .Va net.inet.icmp.maskrepl
203 MIB variable to enable
207 print the origination, reception and transmission timestamps.
209 Set the IP Time To Live for outgoing packets.
210 If not specified, the kernel uses the value of the
215 No attempt will be made to lookup symbolic names for host addresses.
217 Exit successfully after receiving one reply packet.
220 specifies IPsec policy for the ping session.
221 For details please refer to
224 .Xr ipsec_set_policy 3 .
226 You may specify up to 16
228 bytes to fill out the packet you send.
229 This is useful for diagnosing data-dependent problems in a network.
232 will cause the sent packet to be filled with all
235 Somewhat quiet output.
237 display ICMP error messages that are in response to our query messages.
240 flag was required to display such errors, but
242 displays all ICMP error messages.
243 On a busy machine, this output can be overbearing.
248 prints out any ICMP error messages caused by its own ECHO_REQUEST
252 Nothing is displayed except the summary lines at startup time and
261 the route buffer on returned packets.
262 Note that the IP header is only large enough for nine such routes;
265 command is usually better at determining the route packets take to a
266 particular destination.
267 If more routes come back than should, such as due to an illegal spoofed
268 packet, ping will print the route list and then truncate it at the correct
270 Many hosts ignore or discard the
274 Bypass the normal routing tables and send directly to a host on an attached
276 If the host is not on a directly-attached network, an error is returned.
277 This option can be used to ping a local host through an interface
278 that has no route through it
279 (e.g., after the interface was dropped by
282 Use the following IP address as the source address in outgoing packets.
283 On hosts with more than one IP address, this option can be used to
284 force the source address to be something other than the IP address
285 of the interface the probe packet is sent on.
287 is not one of this machine's interface addresses, an error is
288 returned and nothing is sent.
289 .It Fl s Ar packetsize
290 Specify the number of data bytes to be sent.
291 The default is 56, which translates into 64
293 data bytes when combined
297 Only the super-user may specify values more than default.
298 This option cannot be used with ping sweeps.
300 Set the IP Time To Live for multicasted packets.
301 This flag only applies if the ping destination is a multicast address.
303 Specify a timeout, in seconds, before ping exits regardless of how
304 many packets have been received.
310 that are received are listed.
312 Time in milliseconds to wait for a reply for each packet sent.
313 If a reply arrives later, the packet is not printed as replied, but
314 considered as replied when calculating statistics.
316 Use the specified type of service.
321 for fault isolation, it should first be run on the local host, to verify
322 that the local network interface is up and running.
323 Then, hosts and gateways further and further away should be
325 Round-trip times and packet loss statistics are computed.
326 If duplicate packets are received, they are not included in the packet
327 loss calculation, although the round trip time of these packets is used
328 in calculating the round-trip time statistics.
329 When the specified number of packets have been sent
331 or if the program is terminated with a
333 a brief summary is displayed, showing the number of packets sent and
334 received, and the minimum, mean, maximum, and standard deviation of
335 the round-trip times.
345 signal, the current number of packets sent and received, and the
346 minimum, mean, and maximum of the round-trip times will be written to
347 the standard error output.
349 This program is intended for use in network testing, measurement and
351 Because of the load it can impose on the network, it is unwise to use
353 during normal operations or from automated scripts.
354 .Sh ICMP PACKET DETAILS
355 An IP header without options is 20 bytes.
359 packet contains an additional 8 bytes worth of
361 header followed by an arbitrary amount of data.
364 is given, this indicated the size of this extra piece of data
366 Thus the amount of data received inside of an IP packet of type
369 will always be 8 bytes more than the requested data space
374 If the data space is at least eight bytes large,
376 uses the first eight bytes of this space to include a timestamp which
377 it uses in the computation of round trip times.
378 If less than eight bytes of pad are specified, no round trip times are
380 .Sh DUPLICATE AND DAMAGED PACKETS
383 utility will report duplicate and damaged packets.
384 Duplicate packets should never occur when pinging a unicast address,
385 and seem to be caused by
386 inappropriate link-level retransmissions.
387 Duplicates may occur in many situations and are rarely
389 a good sign, although the presence of low levels of duplicates may not
390 always be cause for alarm.
391 Duplicates are expected when pinging a broadcast or multicast address,
392 since they are not really duplicates but replies from different hosts
395 Damaged packets are obviously serious cause for alarm and often
396 indicate broken hardware somewhere in the
398 packet's path (in the network or in the hosts).
399 .Sh TRYING DIFFERENT DATA PATTERNS
402 layer should never treat packets differently depending on the data
403 contained in the data portion.
404 Unfortunately, data-dependent problems have been known to sneak into
405 networks and remain undetected for long periods of time.
406 In many cases the particular pattern that will have problems is something
407 that does not have sufficient
409 such as all ones or all zeros, or a pattern right at the edge, such as
412 necessarily enough to specify a data pattern of all zeros (for example)
413 on the command line because the pattern that is of interest is
414 at the data link level, and the relationship between what you type and
415 what the controllers transmit can be complicated.
417 This means that if you have a data-dependent problem you will probably
418 have to do a lot of testing to find it.
419 If you are lucky, you may manage to find a file that either
421 be sent across your network or that takes much longer to transfer than
422 other similar length files.
423 You can then examine this file for repeated patterns that you can test
431 value of an IP packet represents the maximum number of IP routers
432 that the packet can go through before being thrown away.
433 In current practice you can expect each router in the Internet to decrement
436 field by exactly one.
440 specification recommends setting the
444 packets to 64, but many systems use smaller values
450 The maximum possible value of this field is 255, and most
456 .Tn ICMP ECHO_REQUEST
458 This is why you will find you can
460 some hosts, but not reach them with
467 prints the ttl value from the packet it receives.
468 When a remote system receives a ping packet, it can do one of three things
471 field in its response:
474 Not change it; this is what
476 systems did before the
481 value in the received packet will be 255 minus the
482 number of routers in the round-trip path.
484 Set it to 255; this is what current
489 value in the received packet will be 255 minus the
490 number of routers in the path
498 Set it to some other value.
499 Some machines use the same value for
501 packets that they use for
503 packets, for example either 30 or 60.
504 Others may use completely wild values.
509 utility returns an exit status of zero if at least one response was
510 heard from the specified
512 a status of two if the transmission was successful but no responses
513 were received; or another value
516 if an error occurred.
530 utility was written by
532 while at the US Army Ballistics
535 Many Hosts and Gateways ignore the
539 The maximum IP header length is too small for options like
541 to be completely useful.
543 not much that can be done about this, however.
545 Flood pinging is not recommended in general, and flood pinging the
546 broadcast address should only be done under very controlled conditions.
550 option is not worth much on busy hosts.
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