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32 .\" @(#)ping.8 8.2 (Berkeley) 12/11/93
42 packets to network hosts
51 .Op Fl s Ar packetsize
65 .No protocol Ap s mandatory
68 .Tn ICMP ECHO_RESPONSE
69 from a host or gateway.
77 and then an arbitrary number of
79 bytes used to fill out the packet. The options are as follows:
80 .Bl -tag -width indent
85 character in the output when any packet is received.
86 This option is ignored
87 if other format options are present.
94 If this option is not specified,
96 will operate until interrupted.
100 option on the socket being used.
103 Outputs packets as fast as they come back or one hundred times per second,
109 is printed, while for every
111 received a backspace is printed.
112 This provides a rapid display of how many packets are being dropped.
113 Only the super-user may use this option.
115 This can be very hard on a network and should be used with caution.
121 .Em between sending each packet .
122 The default is to wait for one second between each packet.
123 The wait time may be fractional, but only the super-user may specify
124 values less then 1 second.
125 This option is incompatible with the
128 .It Fl I Ar interface
129 Source multicast packets with the given interface address.
130 This flag only applies if the ping destination is a multicast address.
136 sends that many packets as fast as possible before falling into its normal
138 Only the super-user may use this option.
140 Suppress loopback of multicast packets.
141 This flag only applies if the ping destination is a multicast address.
144 No attempt will be made to lookup symbolic names for host addresses.
146 You may specify up to 16
148 bytes to fill out the packet you send.
149 This is useful for diagnosing data-dependent problems in a network.
152 will cause the sent packet to be filled with all
156 specifies IPsec policy for the ping session.
157 For details please refer to
160 .Xr ipsec_set_policy 3 .
162 Somewhat quiet output.
164 display ICMP error messages that are in response to our query messages.
167 flag was required to display such errors, but
169 displays all ICMP error messages. On a busy machine, this output can
170 be overbearing. Without the
174 prints out any ICMP error messages caused by its own ECHO_REQUEST
178 Nothing is displayed except the summary lines at startup time and
187 the route buffer on returned packets.
188 Note that the IP header is only large enough for nine such routes;
191 command is usually better at determining the route packets take to a
192 particular destination.
193 If more routes come back than should, such as due to an illegal spoofed
194 packet, ping will print the route list and then truncate it at the correct
196 Many hosts ignore or discard the
200 Bypass the normal routing tables and send directly to a host on an attached
202 If the host is not on a directly-attached network, an error is returned.
203 This option can be used to ping a local host through an interface
204 that has no route through it
206 e.g., after the interface was dropped by
209 .It Fl s Ar packetsize
210 Specify the number of data bytes to be sent.
211 The default is 56, which translates into 64
213 data bytes when combined
217 Only the super-user may use this option.
219 Use the following IP address as the source address in outgoing packets.
220 On hosts with more than one IP address, this option can be used to
221 force the source address to be something other than the IP address
222 of the interface the probe packet is sent on. If the IP address
223 is not one of this machine's interface addresses, an error is
224 returned and nothing is sent.
226 Specify a timeout, in seconds, before ping exits regardless of how
227 many packets have been recieved.
229 Set the IP Time To Live for multicasted packets.
230 This flag only applies if the ping destination is a multicast address.
236 that are received are listed.
241 for fault isolation, it should first be run on the local host, to verify
242 that the local network interface is up and running.
243 Then, hosts and gateways further and further away should be
245 Round-trip times and packet loss statistics are computed.
246 If duplicate packets are received, they are not included in the packet
247 loss calculation, although the round trip time of these packets is used
248 in calculating the round-trip time statistics.
249 When the specified number of packets have been sent
251 or if the program is terminated with a
253 a brief summary is displayed, showing the number of packets sent and
254 received, and the minimum, maximum, mean, and standard deviation of
255 the round-trip times.
257 This program is intended for use in network testing, measurement and
259 Because of the load it can impose on the network, it is unwise to use
261 during normal operations or from automated scripts.
262 .Sh ICMP PACKET DETAILS
263 An IP header without options is 20 bytes.
267 packet contains an additional 8 bytes worth of
269 header followed by an arbitrary amount of data.
272 is given, this indicated the size of this extra piece of data
273 .Pq the default is 56 .
274 Thus the amount of data received inside of an IP packet of type
277 will always be 8 bytes more than the requested data space
278 .Pq the Tn ICMP header .
280 If the data space is at least eight bytes large,
282 uses the first eight bytes of this space to include a timestamp which
283 it uses in the computation of round trip times.
284 If less than eight bytes of pad are specified, no round trip times are
286 .Sh DUPLICATE AND DAMAGED PACKETS
288 will report duplicate and damaged packets.
289 Duplicate packets should never occur when pinging a unicast address,
290 and seem to be caused by
291 inappropriate link-level retransmissions.
292 Duplicates may occur in many situations and are rarely
294 a good sign, although the presence of low levels of duplicates may not
295 always be cause for alarm.
296 Duplicates are expected when pinging a broadcast or multicast address,
297 since they are not really duplicates but replies from different hosts
300 Damaged packets are obviously serious cause for alarm and often
301 indicate broken hardware somewhere in the
303 packet's path (in the network or in the hosts).
304 .Sh TRYING DIFFERENT DATA PATTERNS
307 layer should never treat packets differently depending on the data
308 contained in the data portion.
309 Unfortunately, data-dependent problems have been known to sneak into
310 networks and remain undetected for long periods of time.
311 In many cases the particular pattern that will have problems is something
312 that does not have sufficient
314 such as all ones or all zeros, or a pattern right at the edge, such as
317 necessarily enough to specify a data pattern of all zeros (for example)
318 on the command line because the pattern that is of interest is
319 at the data link level, and the relationship between what you type and
320 what the controllers transmit can be complicated.
322 This means that if you have a data-dependent problem you will probably
323 have to do a lot of testing to find it.
324 If you are lucky, you may manage to find a file that either
326 be sent across your network or that takes much longer to transfer than
327 other similar length files.
328 You can then examine this file for repeated patterns that you can test
336 value of an IP packet represents the maximum number of IP routers
337 that the packet can go through before being thrown away.
338 In current practice you can expect each router in the Internet to decrement
341 field by exactly one.
345 specification states that the
349 packets should be set to 60, but many systems use smaller values
357 The maximum possible value of this field is 255, and most
363 .Tn ICMP ECHO_REQUEST
365 This is why you will find you can
367 some hosts, but not reach them with
374 prints the ttl value from the packet it receives.
375 When a remote system receives a ping packet, it can do one of three things
378 field in its response:
381 Not change it; this is what
383 systems did before the
388 value in the received packet will be 255 minus the
389 number of routers in the round-trip path.
391 Set it to 255; this is what current
396 value in the received packet will be 255 minus the
397 number of routers in the path
405 Set it to some other value.
406 Some machines use the same value for
408 packets that they use for
410 packets, for example either 30 or 60.
411 Others may use completely wild values.
416 command returns an exit status of zero if at least one response was
417 heard from the specified
419 a status of two if the transmission was successful but no responses
420 were received; or another value
421 .Pq from Aq Pa sysexits.h
422 if an error occurred.
436 command was written by
438 while at the US Army Ballistics
441 Many Hosts and Gateways ignore the
445 The maximum IP header length is too small for options like
447 to be completely useful.
449 not much that can be done about this, however.
451 Flood pinging is not recommended in general, and flood pinging the
452 broadcast address should only be done under very controlled conditions.
456 option is not worth much on busy hosts.