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32 .\" @(#)ping.8 8.2 (Berkeley) 12/11/93
33 .\" $FreeBSD: src/sbin/ping/ping.8,v 1.25.2.11 2003/02/23 21:03:24 trhodes Exp $
34 .\" $DragonFly: src/sbin/ping/ping.8,v 1.3 2006/03/01 08:08:44 swildner Exp $
36 .Dd September 25, 2001
43 packets to network hosts
53 .Op Fl s Ar packetsize
67 .No protocol Ap s mandatory
70 .Tn ICMP ECHO_RESPONSE
71 from a host or gateway.
79 and then an arbitrary number of
81 bytes used to fill out the packet.
82 The options are as follows:
83 .Bl -tag -width indent
89 character when no packet is received before the next packet
91 To cater for round-trip times that are longer than the interval
92 between transmissions, further missing packets cause a bell only
93 if the maximum number of unreceived packets has increased.
99 character in the output when any packet is received.
100 This option is ignored
101 if other format options are present.
108 If this option is not specified,
110 will operate until interrupted.
114 option on the socket being used.
117 Outputs packets as fast as they come back or one hundred times per second,
123 is printed, while for every
125 received a backspace is printed.
126 This provides a rapid display of how many packets are being dropped.
127 Only the super-user may use this option.
129 This can be very hard on a network and should be used with caution.
135 .Em between sending each packet .
136 The default is to wait for one second between each packet.
137 The wait time may be fractional, but only the super-user may specify
138 values less than 1 second.
139 This option is incompatible with the
142 .It Fl I Ar interface
143 Source multicast packets with the given interface address.
144 This flag only applies if the ping destination is a multicast address.
150 sends that many packets as fast as possible before falling into its normal
152 Only the super-user may use this option.
154 Set the IP Time To Live for outgoing packets.
155 If not specified, the kernel uses the value of the
159 Suppress loopback of multicast packets.
160 This flag only applies if the ping destination is a multicast address.
163 No attempt will be made to lookup symbolic names for host addresses.
165 You may specify up to 16
167 bytes to fill out the packet you send.
168 This is useful for diagnosing data-dependent problems in a network.
171 will cause the sent packet to be filled with all
175 specifies IPsec policy for the ping session.
176 For details please refer to
179 .Xr ipsec_set_policy 3 .
181 Somewhat quiet output.
183 display ICMP error messages that are in response to our query messages.
186 flag was required to display such errors, but
188 displays all ICMP error messages.
189 On a busy machine, this output can
195 prints out any ICMP error messages caused by its own ECHO_REQUEST
199 Nothing is displayed except the summary lines at startup time and
208 the route buffer on returned packets.
209 Note that the IP header is only large enough for nine such routes;
212 command is usually better at determining the route packets take to a
213 particular destination.
214 If more routes come back than should, such as due to an illegal spoofed
215 packet, ping will print the route list and then truncate it at the correct
217 Many hosts ignore or discard the
221 Bypass the normal routing tables and send directly to a host on an attached
223 If the host is not on a directly-attached network, an error is returned.
224 This option can be used to ping a local host through an interface
225 that has no route through it
226 (e.g., after the interface was dropped by
228 .It Fl s Ar packetsize
229 Specify the number of data bytes to be sent.
230 The default is 56, which translates into 64
232 data bytes when combined
236 Only the super-user may use this option.
238 Use the following IP address as the source address in outgoing packets.
239 On hosts with more than one IP address, this option can be used to
240 force the source address to be something other than the IP address
241 of the interface the probe packet is sent on.
242 If the IP address is not one of this machine's interface addresses,
243 an error is returned and nothing is sent.
245 Specify a timeout, in seconds, before ping exits regardless of how
246 many packets have been received.
248 Set the IP Time To Live for multicasted packets.
249 This flag only applies if the ping destination is a multicast address.
255 that are received are listed.
260 for fault isolation, it should first be run on the local host, to verify
261 that the local network interface is up and running.
262 Then, hosts and gateways further and further away should be
264 Round-trip times and packet loss statistics are computed.
265 If duplicate packets are received, they are not included in the packet
266 loss calculation, although the round trip time of these packets is used
267 in calculating the round-trip time statistics.
268 When the specified number of packets have been sent
270 or if the program is terminated with a
272 a brief summary is displayed, showing the number of packets sent and
273 received, and the minimum, mean, maximum, and standard deviation of
274 the round-trip times.
284 signal, the current number of packets sent and received, and the
285 minimum, mean, and maximum of the round-trip times will be written to
286 the standard error output.
288 This program is intended for use in network testing, measurement and
290 Because of the load it can impose on the network, it is unwise to use
292 during normal operations or from automated scripts.
293 .Sh ICMP PACKET DETAILS
294 An IP header without options is 20 bytes.
298 packet contains an additional 8 bytes worth of
300 header followed by an arbitrary amount of data.
303 is given, this indicated the size of this extra piece of data
305 Thus the amount of data received inside of an IP packet of type
308 will always be 8 bytes more than the requested data space
313 If the data space is at least eight bytes large,
315 uses the first eight bytes of this space to include a timestamp which
316 it uses in the computation of round trip times.
317 If less than eight bytes of pad are specified, no round trip times are
319 .Sh DUPLICATE AND DAMAGED PACKETS
321 will report duplicate and damaged packets.
322 Duplicate packets should never occur when pinging a unicast address,
323 and seem to be caused by
324 inappropriate link-level retransmissions.
325 Duplicates may occur in many situations and are rarely
327 a good sign, although the presence of low levels of duplicates may not
328 always be cause for alarm.
329 Duplicates are expected when pinging a broadcast or multicast address,
330 since they are not really duplicates but replies from different hosts
333 Damaged packets are obviously serious cause for alarm and often
334 indicate broken hardware somewhere in the
336 packet's path (in the network or in the hosts).
337 .Sh TRYING DIFFERENT DATA PATTERNS
340 layer should never treat packets differently depending on the data
341 contained in the data portion.
342 Unfortunately, data-dependent problems have been known to sneak into
343 networks and remain undetected for long periods of time.
344 In many cases the particular pattern that will have problems is something
345 that does not have sufficient
347 such as all ones or all zeros, or a pattern right at the edge, such as
350 necessarily enough to specify a data pattern of all zeros (for example)
351 on the command line because the pattern that is of interest is
352 at the data link level, and the relationship between what you type and
353 what the controllers transmit can be complicated.
355 This means that if you have a data-dependent problem you will probably
356 have to do a lot of testing to find it.
357 If you are lucky, you may manage to find a file that either
359 be sent across your network or that takes much longer to transfer than
360 other similar length files.
361 You can then examine this file for repeated patterns that you can test
369 value of an IP packet represents the maximum number of IP routers
370 that the packet can go through before being thrown away.
371 In current practice you can expect each router in the Internet to decrement
374 field by exactly one.
378 specification states that the
382 packets should be set to 60, but many systems use smaller values
388 The maximum possible value of this field is 255, and most
394 .Tn ICMP ECHO_REQUEST
396 This is why you will find you can
398 some hosts, but not reach them with
405 prints the ttl value from the packet it receives.
406 When a remote system receives a ping packet, it can do one of three things
409 field in its response:
412 Not change it; this is what
414 systems did before the
419 value in the received packet will be 255 minus the
420 number of routers in the round-trip path.
422 Set it to 255; this is what current
427 value in the received packet will be 255 minus the
428 number of routers in the path
436 Set it to some other value.
437 Some machines use the same value for
439 packets that they use for
441 packets, for example either 30 or 60.
442 Others may use completely wild values.
447 command returns an exit status of zero if at least one response was
448 heard from the specified
450 a status of two if the transmission was successful but no responses
451 were received; or another value
454 if an error occurred.
468 command was written by
470 while at the US Army Ballistics
473 Many Hosts and Gateways ignore the
477 The maximum IP header length is too small for options like
479 to be completely useful.
481 not much that can be done about this, however.
483 Flood pinging is not recommended in general, and flood pinging the
484 broadcast address should only be done under very controlled conditions.
488 option is not worth much on busy hosts.
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