1PING(8)                             iputils                            PING(8)
2
3
4

NAME

6       ping - send ICMP ECHO_REQUEST to network hosts
7

SYNOPSIS

9       ping [-aAbBdDfhLnOqrRUvV46] [-c count] [-F flowlabel] [-i interval]
10            [-I interface] [-l preload] [-m mark] [-M pmtudisc_option]
11            [-N nodeinfo_option] [-w deadline] [-W timeout] [-p pattern]
12            [-Q tos] [-s packetsize] [-S sndbuf] [-t ttl]
13            [-T timestamp option] [hop...] {destination}
14

DESCRIPTION

16       ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit
17       an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams
18       (“pings”) have an IP and ICMP header, followed by a struct timeval and
19       then an arbitrary number of “pad” bytes used to fill out the packet.
20
21       ping works with both IPv4 and IPv6. Using only one of them explicitly
22       can be enforced by specifying -4 or -6.
23
24       ping can also send IPv6 Node Information Queries (RFC4620).
25       Intermediate hops may not be allowed, because IPv6 source routing was
26       deprecated (RFC5095).
27

OPTIONS

29       -4
30           Use IPv4 only.
31
32       -6
33           Use IPv6 only.
34
35       -a
36           Audible ping.
37
38       -A
39           Adaptive ping. Interpacket interval adapts to round-trip time, so
40           that effectively not more than one (or more, if preload is set)
41           unanswered probe is present in the network. Minimal interval is
42           200msec for not super-user. On networks with low rtt this mode is
43           essentially equivalent to flood mode.
44
45       -b
46           Allow pinging a broadcast address.
47
48       -B
49           Do not allow ping to change source address of probes. The address
50           is bound to one selected when ping starts.
51
52       -c count
53           Stop after sending count ECHO_REQUEST packets. With deadline
54           option, ping waits for count ECHO_REPLY packets, until the timeout
55           expires.
56
57       -d
58           Set the SO_DEBUG option on the socket being used. Essentially, this
59           socket option is not used by Linux kernel.
60
61       -D
62           Print timestamp (unix time + microseconds as in gettimeofday)
63           before each line.
64
65       -f
66           Flood ping. For every ECHO_REQUEST sent a period “.” is printed,
67           while for ever ECHO_REPLY received a backspace is printed. This
68           provides a rapid display of how many packets are being dropped. If
69           interval is not given, it sets interval to zero and outputs packets
70           as fast as they come back or one hundred times per second,
71           whichever is more. Only the super-user may use this option with
72           zero interval.
73
74       -F flow label
75           IPv6 only. Allocate and set 20 bit flow label (in hex) on echo
76           request packets. If value is zero, kernel allocates random flow
77           label.
78
79       -h
80           Show help.
81
82       -i interval
83           Wait interval seconds between sending each packet. The default is
84           to wait for one second between each packet normally, or not to wait
85           in flood mode. Only super-user may set interval to values less than
86           0.2 seconds.
87
88       -I interface
89           interface is either an address, or an interface name. If interface
90           is an address, it sets source address to specified interface
91           address. If interface in an interface name, it sets source
92           interface to specified interface. NOTE: For IPv6, when doing ping
93           to a link-local scope address, link specification (by the
94           '%'-notation in destination, or by this option) can be used but it
95           is no longer required.
96
97       -l preload
98           If preload is specified, ping sends that many packets not waiting
99           for reply. Only the super-user may select preload more than 3.
100
101       -L
102           Suppress loopback of multicast packets. This flag only applies if
103           the ping destination is a multicast address.
104
105       -m mark
106           use mark to tag the packets going out. This is useful for variety
107           of reasons within the kernel such as using policy routing to select
108           specific outbound processing.
109
110       -M pmtudisc_opt
111           Select Path MTU Discovery strategy.  pmtudisc_option may be either
112           do (prohibit fragmentation, even local one), want (do PMTU
113           discovery, fragment locally when packet size is large), or dont (do
114           not set DF flag).
115
116       -N nodeinfo_option
117           IPv6 only. Send ICMPv6 Node Information Queries (RFC4620), instead
118           of Echo Request. CAP_NET_RAW capability is required.
119
120           help
121               Show help for NI support.
122
123           name
124               Queries for Node Names.
125
126           ipv6
127               Queries for IPv6 Addresses. There are several IPv6 specific
128               flags.
129
130               ipv6-global
131                   Request IPv6 global-scope addresses.
132
133               ipv6-sitelocal
134                   Request IPv6 site-local addresses.
135
136               ipv6-linklocal
137                   Request IPv6 link-local addresses.
138
139               ipv6-all
140                   Request IPv6 addresses on other interfaces.
141
142           ipv4
143               Queries for IPv4 Addresses. There is one IPv4 specific flag.
144
145               ipv4-all
146                   Request IPv4 addresses on other interfaces.
147
148           subject-ipv6=ipv6addr
149               IPv6 subject address.
150
151           subject-ipv4=ipv4addr
152               IPv4 subject address.
153
154           subject-name=nodename
155               Subject name. If it contains more than one dot, fully-qualified
156               domain name is assumed.
157
158           subject-fqdn=nodename
159               Subject name. Fully-qualified domain name is always assumed.
160
161       -n
162           Numeric output only. No attempt will be made to lookup symbolic
163           names for host addresses.
164
165       -O
166           Report outstanding ICMP ECHO reply before sending next packet. This
167           is useful together with the timestamp -D to log output to a
168           diagnostic file and search for missing answers.
169
170       -p pattern
171           You may specify up to 16 “pad” bytes to fill out the packet you
172           send. This is useful for diagnosing data-dependent problems in a
173           network. For example, -p ff will cause the sent packet to be filled
174           with all ones.
175
176       -q
177           Quiet output. Nothing is displayed except the summary lines at
178           startup time and when finished.
179
180       -Q tos
181           Set Quality of Service -related bits in ICMP datagrams.  tos can be
182           decimal (ping only) or hex number.
183
184           In RFC2474, these fields are interpreted as 8-bit Differentiated
185           Services (DS), consisting of: bits 0-1 (2 lowest bits) of separate
186           data, and bits 2-7 (highest 6 bits) of Differentiated Services
187           Codepoint (DSCP). In RFC2481 and RFC3168, bits 0-1 are used for
188           ECN.
189
190           Historically (RFC1349, obsoleted by RFC2474), these were
191           interpreted as: bit 0 (lowest bit) for reserved (currently being
192           redefined as congestion control), 1-4 for Type of Service and bits
193           5-7 (highest bits) for Precedence.
194
195       -r
196           Bypass the normal routing tables and send directly to a host on an
197           attached interface. If the host is not on a directly-attached
198           network, an error is returned. This option can be used to ping a
199           local host through an interface that has no route through it
200           provided the option -I is also used.
201
202       -R
203           ping only. Record route. Includes the RECORD_ROUTE option in the
204           ECHO_REQUEST packet and displays the route buffer on returned
205           packets. Note that the IP header is only large enough for nine such
206           routes. Many hosts ignore or discard this option.
207
208       -s packetsize
209           Specifies the number of data bytes to be sent. The default is 56,
210           which translates into 64 ICMP data bytes when combined with the 8
211           bytes of ICMP header data.
212
213       -S sndbuf
214           Set socket sndbuf. If not specified, it is selected to buffer not
215           more than one packet.
216
217       -t ttl
218           ping only. Set the IP Time to Live.
219
220       -T timestamp option
221           Set special IP timestamp options.  timestamp option may be either
222           tsonly (only timestamps), tsandaddr (timestamps and addresses) or
223           tsprespec host1 [host2 [host3 [host4]]] (timestamp prespecified
224           hops).
225
226       -U
227           Print full user-to-user latency (the old behaviour). Normally ping
228           prints network round trip time, which can be different f.e. due to
229           DNS failures.
230
231       -v
232           Verbose output.
233
234       -V
235           Show version and exit.
236
237       -w deadline
238           Specify a timeout, in seconds, before ping exits regardless of how
239           many packets have been sent or received. In this case ping does not
240           stop after count packet are sent, it waits either for deadline
241           expire or until count probes are answered or for some error
242           notification from network.
243
244       -W timeout
245           Time to wait for a response, in seconds. The option affects only
246           timeout in absence of any responses, otherwise ping waits for two
247           RTTs.
248
249       When using ping for fault isolation, it should first be run on the
250       local host, to verify that the local network interface is up and
251       running. Then, hosts and gateways further and further away should be
252       “pinged”. Round-trip times and packet loss statistics are computed. If
253       duplicate packets are received, they are not included in the packet
254       loss calculation, although the round trip time of these packets is used
255       in calculating the minimum/average/maximum/mdev round-trip time
256       numbers.
257
258       Population standard deviation (mdev), essentially an average of how far
259       each ping RTT is from the mean RTT. The higher mdev is, the more
260       variable the RTT is (over time). With a high RTT variability, you will
261       have speed issues with bulk transfers (they will take longer than is
262       strictly speaking necessary, as the variability will eventually cause
263       the sender to wait for ACKs) and you will have middling to poor VoIP
264       quality.
265
266       When the specified number of packets have been sent (and received) or
267       if the program is terminated with a SIGINT, a brief summary is
268       displayed. Shorter current statistics can be obtained without
269       termination of process with signal SIGQUIT.
270
271       If ping does not receive any reply packets at all it will exit with
272       code 1. If a packet count and deadline are both specified, and fewer
273       than count packets are received by the time the deadline has arrived,
274       it will also exit with code 1. On other error it exits with code 2.
275       Otherwise it exits with code 0. This makes it possible to use the exit
276       code to see if a host is alive or not.
277
278       This program is intended for use in network testing, measurement and
279       management. Because of the load it can impose on the network, it is
280       unwise to use ping during normal operations or from automated scripts.
281

ICMP PACKET DETAILS

283       An IP header without options is 20 bytes. An ICMP ECHO_REQUEST packet
284       contains an additional 8 bytes worth of ICMP header followed by an
285       arbitrary amount of data. When a packetsize is given, this indicated
286       the size of this extra piece of data (the default is 56). Thus the
287       amount of data received inside of an IP packet of type ICMP ECHO_REPLY
288       will always be 8 bytes more than the requested data space (the ICMP
289       header).
290
291       If the data space is at least of size of struct timeval ping uses the
292       beginning bytes of this space to include a timestamp which it uses in
293       the computation of round trip times. If the data space is shorter, no
294       round trip times are given.
295

DUPLICATE AND DAMAGED PACKETS

297       ping will report duplicate and damaged packets. Duplicate packets
298       should never occur, and seem to be caused by inappropriate link-level
299       retransmissions. Duplicates may occur in many situations and are rarely
300       (if ever) a good sign, although the presence of low levels of
301       duplicates may not always be cause for alarm.
302
303       Damaged packets are obviously serious cause for alarm and often
304       indicate broken hardware somewhere in the ping packet's path (in the
305       network or in the hosts).
306

TRYING DIFFERENT DATA PATTERNS

308       The (inter)network layer should never treat packets differently
309       depending on the data contained in the data portion. Unfortunately,
310       data-dependent problems have been known to sneak into networks and
311       remain undetected for long periods of time. In many cases the
312       particular pattern that will have problems is something that doesn't
313       have sufficient “transitions”, such as all ones or all zeros, or a
314       pattern right at the edge, such as almost all zeros. It isn't
315       necessarily enough to specify a data pattern of all zeros (for example)
316       on the command line because the pattern that is of interest is at the
317       data link level, and the relationship between what you type and what
318       the controllers transmit can be complicated.
319
320       This means that if you have a data-dependent problem you will probably
321       have to do a lot of testing to find it. If you are lucky, you may
322       manage to find a file that either can't be sent across your network or
323       that takes much longer to transfer than other similar length files. You
324       can then examine this file for repeated patterns that you can test
325       using the -p option of ping.
326

TTL DETAILS

328       The TTL value of an IP packet represents the maximum number of IP
329       routers that the packet can go through before being thrown away. In
330       current practice you can expect each router in the Internet to
331       decrement the TTL field by exactly one.
332
333       The TCP/IP specification states that the TTL field for TCP packets
334       should be set to 60, but many systems use smaller values (4.3 BSD uses
335       30, 4.2 used 15).
336
337       The maximum possible value of this field is 255, and most Unix systems
338       set the TTL field of ICMP ECHO_REQUEST packets to 255. This is why you
339       will find you can “ping” some hosts, but not reach them with telnet(1)
340       or ftp(1).
341
342       In normal operation ping prints the TTL value from the packet it
343       receives. When a remote system receives a ping packet, it can do one of
344       three things with the TTL field in its response:
345
346           · Not change it; this is what Berkeley Unix systems did before the
347           4.3BSD Tahoe release. In this case the TTL value in the received
348           packet will be 255 minus the number of routers in the round-trip
349           path.
350
351           · Set it to 255; this is what current Berkeley Unix systems do. In
352           this case the TTL value in the received packet will be 255 minus
353           the number of routers in the path from the remote system to the
354           pinging host.
355
356           · Set it to some other value. Some machines use the same value for
357           ICMP packets that they use for TCP packets, for example either 30
358           or 60. Others may use completely wild values.
359

BUGS

361           · Many Hosts and Gateways ignore the RECORD_ROUTE option.
362
363           · The maximum IP header length is too small for options like
364           RECORD_ROUTE to be completely useful. There's not much that can be
365           done about this, however.
366
367           · Flood pinging is not recommended in general, and flood pinging
368           the broadcast address should only be done under very controlled
369           conditions.
370

SEE ALSO

372       ip(8), ss(8).
373

HISTORY

375       The ping command appeared in 4.3BSD.
376
377       The version described here is its descendant specific to Linux.
378
379       As of version s20150815, the ping6 binary doesn't exist anymore. It has
380       been merged into ping. Creating a symlink named ping6 pointing to ping
381       will result in the same funcionality as before.
382

SECURITY

384       ping requires CAP_NET_RAW capability to be executed 1) if the program
385       is used for non-echo queries (See -N option), or 2) if kernel does not
386       support non-raw ICMP sockets, or 3) if the user is not allowed to
387       create an ICMP echo socket. The program may be used as set-uid root.
388

AVAILABILITY

390       ping is part of iputils package.
391
392
393
394iputils s20190515                                                      PING(8)
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