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28 .\" @(#)ping.8 8.2 (Berkeley) 12/11/93
29 .\" $FreeBSD: /repoman/r/ncvs/src/sbin/ping/ping.8,v 1.51 2004/04/09 19:58:34 markm Exp $
38 packets to network hosts
45 .Op Fl M Cm mask | time
50 .Op Fl s Ar packetsize
60 .Op Fl M Cm mask | time
65 .Op Fl s Ar packetsize
75 .No protocol Ap s mandatory
78 .Tn ICMP ECHO_RESPONSE
79 from a host or gateway.
87 and then an arbitrary number of
89 bytes used to fill out the packet.
90 The options are as follows:
91 .Bl -tag -width indent
97 character when no packet is received before the next packet
99 To cater for round-trip times that are longer than the interval
100 between transmissions, further missing packets cause a bell only
101 if the maximum number of unreceived packets has increased.
107 character in the output when any packet is received.
108 This option is ignored
109 if other format options are present.
116 If this option is not specified,
118 will operate until interrupted.
120 Set the Don't Fragment bit.
124 option on the socket being used.
127 Outputs packets as fast as they come back or one hundred times per second,
133 is printed, while for every
135 received a backspace is printed.
136 This provides a rapid display of how many packets are being dropped.
137 Only the super-user may use this option.
139 This can be very hard on a network and should be used with caution.
142 Source multicast packets with the given interface address.
143 This flag only applies if the ping destination is a multicast address.
148 .Em between sending each packet .
149 The default is to wait for one second between each packet.
150 The wait time may be fractional, but only the super-user may specify
151 values less than 1 second.
152 This option is incompatible with the
156 Suppress loopback of multicast packets.
157 This flag only applies if the ping destination is a multicast address.
163 sends that many packets as fast as possible before falling into its normal
165 Only the super-user may use this option.
166 .It Fl M Cm mask | time
175 print the netmask of the remote machine.
177 .Va net.inet.icmp.maskrepl
178 MIB variable to enable
182 print the origination, reception and transmission timestamps.
184 Set the IP Time To Live for outgoing packets.
185 If not specified, the kernel uses the value of the
190 No attempt will be made to lookup symbolic names for host addresses.
192 Exit successfully after receiving one reply packet.
195 specifies IPsec policy for the ping session.
196 For details please refer to
199 .Xr ipsec_set_policy 3 .
201 You may specify up to 16
203 bytes to fill out the packet you send.
204 This is useful for diagnosing data-dependent problems in a network.
207 will cause the sent packet to be filled with all
210 Somewhat quiet output.
212 display ICMP error messages that are in response to our query messages.
215 flag was required to display such errors, but
217 displays all ICMP error messages.
218 On a busy machine, this output can be overbearing.
223 prints out any ICMP error messages caused by its own ECHO_REQUEST
227 Nothing is displayed except the summary lines at startup time and
236 the route buffer on returned packets.
237 Note that the IP header is only large enough for nine such routes;
240 command is usually better at determining the route packets take to a
241 particular destination.
242 If more routes come back than should, such as due to an illegal spoofed
243 packet, ping will print the route list and then truncate it at the correct
245 Many hosts ignore or discard the
249 Bypass the normal routing tables and send directly to a host on an attached
251 If the host is not on a directly-attached network, an error is returned.
252 This option can be used to ping a local host through an interface
253 that has no route through it
254 (e.g., after the interface was dropped by
257 Use the following IP address as the source address in outgoing packets.
258 On hosts with more than one IP address, this option can be used to
259 force the source address to be something other than the IP address
260 of the interface the probe packet is sent on.
262 is not one of this machine's interface addresses, an error is
263 returned and nothing is sent.
264 .It Fl s Ar packetsize
265 Specify the number of data bytes to be sent.
266 The default is 56, which translates into 64
268 data bytes when combined
273 Set the IP Time To Live for multicasted packets.
274 This flag only applies if the ping destination is a multicast address.
276 Specify a timeout, in seconds, before ping exits regardless of how
277 many packets have been received.
283 that are received are listed.
285 Use the specified type of service.
290 for fault isolation, it should first be run on the local host, to verify
291 that the local network interface is up and running.
292 Then, hosts and gateways further and further away should be
294 Round-trip times and packet loss statistics are computed.
295 If duplicate packets are received, they are not included in the packet
296 loss calculation, although the round trip time of these packets is used
297 in calculating the round-trip time statistics.
298 When the specified number of packets have been sent
300 or if the program is terminated with a
302 a brief summary is displayed, showing the number of packets sent and
303 received, and the minimum, mean, maximum, and standard deviation of
304 the round-trip times.
314 signal, the current number of packets sent and received, and the
315 minimum, mean, and maximum of the round-trip times will be written to
316 the standard error output.
318 This program is intended for use in network testing, measurement and
320 Because of the load it can impose on the network, it is unwise to use
322 during normal operations or from automated scripts.
323 .Sh ICMP PACKET DETAILS
324 An IP header without options is 20 bytes.
328 packet contains an additional 8 bytes worth of
330 header followed by an arbitrary amount of data.
333 is given, this indicated the size of this extra piece of data
335 Thus the amount of data received inside of an IP packet of type
338 will always be 8 bytes more than the requested data space
343 If the data space is at least eight bytes large,
345 uses the first eight bytes of this space to include a timestamp which
346 it uses in the computation of round trip times.
347 If less than eight bytes of pad are specified, no round trip times are
349 .Sh DUPLICATE AND DAMAGED PACKETS
352 utility will report duplicate and damaged packets.
353 Duplicate packets should never occur when pinging a unicast address,
354 and seem to be caused by
355 inappropriate link-level retransmissions.
356 Duplicates may occur in many situations and are rarely
358 a good sign, although the presence of low levels of duplicates may not
359 always be cause for alarm.
360 Duplicates are expected when pinging a broadcast or multicast address,
361 since they are not really duplicates but replies from different hosts
364 Damaged packets are obviously serious cause for alarm and often
365 indicate broken hardware somewhere in the
367 packet's path (in the network or in the hosts).
368 .Sh TRYING DIFFERENT DATA PATTERNS
371 layer should never treat packets differently depending on the data
372 contained in the data portion.
373 Unfortunately, data-dependent problems have been known to sneak into
374 networks and remain undetected for long periods of time.
375 In many cases the particular pattern that will have problems is something
376 that does not have sufficient
378 such as all ones or all zeros, or a pattern right at the edge, such as
381 necessarily enough to specify a data pattern of all zeros (for example)
382 on the command line because the pattern that is of interest is
383 at the data link level, and the relationship between what you type and
384 what the controllers transmit can be complicated.
386 This means that if you have a data-dependent problem you will probably
387 have to do a lot of testing to find it.
388 If you are lucky, you may manage to find a file that either
390 be sent across your network or that takes much longer to transfer than
391 other similar length files.
392 You can then examine this file for repeated patterns that you can test
400 value of an IP packet represents the maximum number of IP routers
401 that the packet can go through before being thrown away.
402 In current practice you can expect each router in the Internet to decrement
405 field by exactly one.
409 specification recommends setting the
413 packets to 64, but many systems use smaller values
419 The maximum possible value of this field is 255, and most
425 .Tn ICMP ECHO_REQUEST
427 This is why you will find you can
429 some hosts, but not reach them with
436 prints the ttl value from the packet it receives.
437 When a remote system receives a ping packet, it can do one of three things
440 field in its response:
443 Not change it; this is what
445 systems did before the
450 value in the received packet will be 255 minus the
451 number of routers in the round-trip path.
453 Set it to 255; this is what current
458 value in the received packet will be 255 minus the
459 number of routers in the path
467 Set it to some other value.
468 Some machines use the same value for
470 packets that they use for
472 packets, for example either 30 or 60.
473 Others may use completely wild values.
478 utility returns an exit status of zero if at least one response was
479 heard from the specified
481 a status of two if the transmission was successful but no responses
482 were received; or another value
485 if an error occurred.
499 utility was written by
501 while at the US Army Ballistics
504 Many Hosts and Gateways ignore the
508 The maximum IP header length is too small for options like
510 to be completely useful.
512 not much that can be done about this, however.
514 Flood pinging is not recommended in general, and flood pinging the
515 broadcast address should only be done under very controlled conditions.
519 option is not worth much on busy hosts.
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