xref: /freebsd/sbin/ping/ping.8 (revision ee12faa062c04a49bf6fe4e6867bad8606e2413f)
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28.\"     @(#)ping.8	8.2 (Berkeley) 12/11/93
29.\"
30.Dd November 20, 2022
31.Dt PING 8
32.Os
33.Sh NAME
34.Nm ping
35.Nd send
36ICMP
37or
38ICMPv6 ECHO_REQUEST
39packets to network hosts
40.Sh SYNOPSIS
41.Nm
42.Op Fl 4AaDdfHnoQqRrv
43.Op Fl .\& Ns Ar chars
44.Op Fl C Ar pcp
45.Op Fl c Ar count
46.Op Fl G Ar sweepmaxsize
47.Op Fl g Ar sweepminsize
48.Op Fl h Ar sweepincrsize
49.Op Fl i Ar wait
50.Op Fl l Ar preload
51.Op Fl M Cm mask | time
52.Op Fl m Ar ttl
53.Op Fl P Ar policy
54.Op Fl p Ar pattern
55.Op Fl S Ar src_addr
56.Op Fl s Ar packetsize
57.Op Fl t Ar timeout
58.Op Fl W Ar waittime
59.Op Fl z Ar tos
60.Ar IPv4-host
61.Nm
62.Op Fl 4AaDdfHLnoQqRrv
63.Op Fl .\& Ns Ar chars
64.Op Fl C Ar pcp
65.Op Fl c Ar count
66.Op Fl I Ar iface
67.Op Fl i Ar wait
68.Op Fl l Ar preload
69.Op Fl M Cm mask | time
70.Op Fl m Ar ttl
71.Op Fl P Ar policy
72.Op Fl p Ar pattern
73.Op Fl S Ar src_addr
74.Op Fl s Ar packetsize
75.Op Fl T Ar ttl
76.Op Fl t Ar timeout
77.Op Fl W Ar waittime
78.Op Fl z Ar tos
79.Ar IPv4-mcast-group
80.Nm
81.Op Fl 6AaDdEfHNnOoquvYyZ
82.Op Fl .\& Ns Ar chars
83.Op Fl b Ar bufsiz
84.Op Fl c Ar count
85.Op Fl e Ar gateway
86.Op Fl I Ar interface
87.Op Fl i Ar wait
88.Op Fl k Ar addrtype
89.Op Fl l Ar preload
90.Op Fl m Ar hoplimit
91.Op Fl P Ar policy
92.Op Fl p Ar pattern
93.Op Fl S Ar sourceaddr
94.Op Fl s Ar packetsize
95.Op Fl t Ar timeout
96.Op Fl W Ar waittime
97.Op Ar IPv6-hops ...
98.Ar IPv6-host
99.Sh DESCRIPTION
100The
101.Nm
102utility invoked with an IPv4 target
103.Ar ( IPv4-host
104or
105.Ar IPv4-mcast-group )
106uses the
107ICMP
108.No protocol Ap s mandatory
109ECHO_REQUEST
110datagram to elicit an
111ICMP ECHO_RESPONSE
112from a host or gateway.
113ECHO_REQUEST
114datagrams
115.Pq Dq pings
116have an IP and
117ICMP
118header, followed by a
119.Dq struct timeval
120and then an arbitrary number of
121.Dq pad
122bytes used to fill out the packet.
123.Pp
124When invoked with an IPv6 target
125.Ar ( IPv6-host ) ,
126it uses the
127ICMPv6
128protocol's mandatory
129ICMP6_ECHO_REQUEST
130datagram to elicit an
131ICMP6_ECHO_REPLY.
132ICMP6_ECHO_REQUEST
133datagrams have an IPv6 header and
134ICMPv6
135header formatted as documented in RFC 2463.
136.Pp
137When invoked with a hostname, the version to which the target is resolved first
138is used.
139In that case, the options and arguments used must be valid for the specific IP
140version, otherwise
141.Nm
142exits with an error.
143If the target is resolved to both IPv4 and IPv6, the specific IP version can be
144requested by
145.Fl 4
146or
147.Fl 6
148options, respectively.
149For backwards-compatibility, ICMPv6 can also be selected by invoking the binary
150as
151.Nm ping6 .
152.Ss Options common to both IPv4 and IPv6 targets
153.Bl -tag -width indent
154.It Fl .\& Ns Ar chars
155By default, for every
156ECHO_REQUEST
157sent, a period
158.Dq .\&
159is printed, while for every
160ECHO_REPLY
161received, a backspace is printed.
162This option takes an optional string argument listing characters
163that will be printed one by one in the provided order
164instead of the default period.
165.Pp
166Example usage:
167.Bd -literal -offset indent
168ping -.0123456789 freebsd.org
169.Ed
170.It Fl A
171Audible.
172Output a bell
173(ASCII
1740x07)
175character when no packet is received before the next packet
176is transmitted.
177To cater for round-trip times that are longer than the interval
178between transmissions, further missing packets cause a bell only
179if the maximum number of unreceived packets has increased.
180.It Fl a
181Audible.
182Include a bell
183(ASCII
1840x07)
185character in the output when any packet is received.
186.It Fl C Ar pcp
187Add an 802.1p Ethernet Priority Code Point when sending a packet.
1880..7 uses that specific PCP, -1 uses the interface default PCP (or none).
189.It Fl c Ar count
190Stop after sending
191(and receiving)
192.Ar count
193ECHO_RESPONSE
194packets.
195If this option is not specified,
196.Nm
197will operate until interrupted.
198.Pp
199For an IPv4 target, if this option is specified in conjunction with ping sweeps,
200each sweep will consist of
201.Ar count
202packets.
203.It Fl D
204Disable fragmentation.
205.It Fl d
206Set the
207.Dv SO_DEBUG
208option on the socket being used.
209.It Fl f
210Flood ping.
211Outputs packets as fast as they come back or one hundred times per second,
212whichever is more.
213Implies
214.Fl .\&
215to print a period for every
216ECHO_REQUEST
217sent and a backspace for every
218ECHO_REPLY
219received.
220This provides a rapid display of how many packets are being dropped.
221Only the super-user may use this option.
222.Bf -emphasis
223This can be very hard on a network and should be used with caution.
224.Ef
225.It Fl H
226Hostname output.
227Try to do a reverse DNS lookup when displaying addresses.
228This is the opposite of the
229.Fl n
230option.
231.It Fl I Ar iface
232For an IPv4 target,
233.Ar iface
234is an IP address indentifying an interface from which the packets will be sent.
235This flag applies only if the ping target is a multicast address.
236.Pp
237For an IPv6 target,
238.Ar iface
239is a name of an interface (e.g., `em0') from which the packets will be sent.
240This flag applies if the ping target is a multicast address, or
241link-local/site-local unicast address.
242.It Fl i Ar wait
243Wait
244.Ar wait
245seconds
246.Em between sending each packet .
247The default is to wait for one second between each packet.
248The wait time may be fractional, but only the super-user may specify
249values less than 1 second.
250This option is incompatible with the
251.Fl f
252option.
253.It Fl l Ar preload
254If
255.Ar preload
256is specified,
257.Nm
258sends that many packets as fast as possible before falling into its normal
259mode of behavior.
260Only the super-user may use this option.
261.It Fl m Ar ttl
262For an IPv4 target, set the IP Time To Live for outgoing packets.
263If not specified, the kernel uses the value of the
264.Va net.inet.ip.ttl
265MIB variable.
266.Pp
267For an IPv6 target, set the IPv6 hoplimit.
268.It Fl n
269Numeric output only.
270No attempt will be made to lookup symbolic names for host addresses.
271This is the opposite of
272.Fl H ,
273and it is the default behavior.
274.It Fl o
275Exit successfully after receiving one reply packet.
276.It Fl P Ar policy
277.Ar policy
278specifies IPsec policy for the ping session.
279For details please refer to
280.Xr ipsec 4
281and
282.Xr ipsec_set_policy 3 .
283.It Fl p Ar pattern
284You may specify up to 16
285.Dq pad
286bytes to fill out the packet you send.
287This is useful for diagnosing data-dependent problems in a network.
288For example,
289.Dq Li \-p ff
290will cause the sent packet to be filled with all
291ones.
292.It Fl q
293Quiet output.
294Nothing is displayed except the summary lines at startup time and
295when finished.
296.It Fl S Ar src_addr
297Use the following IP address as the source address in outgoing packets.
298On hosts with more than one IP address, this option can be used to
299force the source address to be something other than the IP address
300of the interface the probe packet is sent on.
301.Pp
302For IPv4, if the IP address is not one of this machine's interface
303addresses, an error is returned and nothing is sent.
304.Pp
305For IPv6, the source address must be one of the unicast addresses of
306the sending node, and must be numeric.
307.It Fl s Ar packetsize
308Specify the number of data bytes to be sent.
309The default is 56, which translates into 64
310ICMP
311data bytes when combined
312with the 8 bytes of
313ICMP
314header data.
315.Pp
316For IPv4, only the super-user may specify values more than default.
317This option cannot be used with ping sweeps.
318.Pp
319For IPv6, you may need to specify
320.Fl b
321as well to extend socket buffer size.
322.It Fl t Ar timeout
323Specify a timeout, in seconds, before ping exits regardless of how
324many packets have been received.
325.It Fl v
326Verbose output.
327ICMP
328packets other than
329ECHO_RESPONSE
330that are received are listed.
331.It Fl W Ar waittime
332Time in milliseconds to wait for a reply for each packet sent.
333If a reply arrives later, the packet is not printed as replied, but
334considered as replied when calculating statistics.
335.El
336.Ss Options only for IPv4 targets
337.Bl -tag -width indent
338.It Fl 4
339Use IPv4 regardless of how the target is resolved.
340.It Fl G Ar sweepmaxsize
341Specify the maximum size of
342ICMP
343payload when sending sweeping pings.
344This option is required for ping sweeps.
345.It Fl g Ar sweepminsize
346Specify the size of
347ICMP
348payload to start with when sending sweeping pings.
349The default value is 0.
350.It Fl h Ar sweepincrsize
351Specify the number of bytes to increment the size of
352ICMP
353payload after
354each sweep when sending sweeping pings.
355The default value is 1.
356.It Fl L
357Suppress loopback of multicast packets.
358This flag only applies if the ping destination is a multicast address.
359.It Fl M Cm mask | time
360Use
361.Dv ICMP_MASKREQ
362or
363.Dv ICMP_TSTAMP
364instead of
365.Dv ICMP_ECHO .
366For
367.Cm mask ,
368print the netmask of the remote machine.
369Set the
370.Va net.inet.icmp.maskrepl
371MIB variable to enable
372.Dv ICMP_MASKREPLY
373and
374.Va net.inet.icmp.maskfake
375if you want to override the netmask in the response.
376For
377.Cm time ,
378print the origination, reception and transmission timestamps.
379Set the
380.Va net.inet.icmp.tstamprepl
381MIB variable to enable or disable
382.Dv ICMP_TSTAMPREPLY .
383.It Fl Q
384Somewhat quiet output.
385.No Don Ap t
386display ICMP error messages that are in response to our query messages.
387Originally, the
388.Fl v
389flag was required to display such errors, but
390.Fl v
391displays all ICMP error messages.
392On a busy machine, this output can be overbearing.
393Without the
394.Fl Q
395flag,
396.Nm
397prints out any ICMP error messages caused by its own ECHO_REQUEST
398messages.
399.It Fl R
400Record route.
401Includes the
402RECORD_ROUTE
403option in the
404ECHO_REQUEST
405packet and displays
406the route buffer on returned packets.
407Note that the IP header is only large enough for nine such routes;
408the
409.Xr traceroute 8
410command is usually better at determining the route packets take to a
411particular destination.
412If more routes come back than should, such as due to an illegal spoofed
413packet, ping will print the route list and then truncate it at the correct
414spot.
415Many hosts ignore or discard the
416RECORD_ROUTE
417option.
418.It Fl r
419Bypass the normal routing tables and send directly to a host on an attached
420network.
421If the host is not on a directly-attached network, an error is returned.
422This option can be used to ping a local host through an interface
423that has no route through it
424(e.g., after the interface was dropped by
425.Xr routed 8 ) .
426.It Fl T Ar ttl
427Set the IP Time To Live for multicasted packets.
428This flag only applies if the ping destination is a multicast address.
429.It Fl z Ar tos
430Use the specified type of service.
431.It Ar IPv4-host
432hostname or IPv4 address of the final destination node.
433.It Ar IPv4-mcast-group
434IPv4 multicast address of the final destination nodes.
435.El
436.Ss Options only for IPv6 targets
437.Bl -tag -width indent
438.It Fl 6
439Use IPv6 regardless of how the target is resolved.
440.It Fl b Ar bufsiz
441Set socket buffer size.
442.It Fl e Ar gateway
443Specifies to use
444.Ar gateway
445as the next hop to the destination.
446The gateway must be a neighbor of the sending node.
447.It Fl k Ar addrtype
448Generate ICMPv6 Node Information Node Addresses query, rather than echo-request.
449.Ar addrtype
450must be a string constructed of the following characters.
451.Bl -tag -width Ds -compact
452.It Ic a
453requests unicast addresses from all of the responder's interfaces.
454If the character is omitted,
455only those addresses which belong to the interface which has the
456responder's address are requests.
457.It Ic c
458requests responder's IPv4-compatible and IPv4-mapped addresses.
459.It Ic g
460requests responder's global-scope addresses.
461.It Ic s
462requests responder's site-local addresses.
463.It Ic l
464requests responder's link-local addresses.
465.It Ic A
466requests responder's anycast addresses.
467Without this character, the responder will return unicast addresses only.
468With this character, the responder will return anycast addresses only.
469Note that the specification does not specify how to get responder's
470anycast addresses.
471This is an experimental option.
472.El
473.It Fl N
474Probe node information multicast group address
475.Pq Li ff02::2:ffxx:xxxx .
476.Ar host
477must be string hostname of the target
478(must not be a numeric IPv6 address).
479Node information multicast group will be computed based on given
480.Ar host ,
481and will be used as the final destination.
482Since node information multicast group is a link-local multicast group,
483outgoing interface needs to be specified by
484.Fl I
485option.
486.Pp
487When specified twice, the address
488.Pq Li ff02::2:xxxx:xxxx
489is used instead.
490The former is in RFC 4620, the latter is in an old Internet Draft
491draft-ietf-ipngwg-icmp-name-lookup.
492Note that KAME-derived implementations including
493.Fx
494use the latter.
495.It Fl O
496Generate ICMPv6 Node Information supported query types query,
497rather than echo-request.
498.Fl s
499has no effect if
500.Fl O
501is specified.
502.It Fl u
503By default,
504.Nm
505asks the kernel to fragment packets to fit into the minimum IPv6 MTU.
506The
507.Fl u
508option
509will suppress the behavior in the following two levels:
510when the option is specified once, the behavior will be disabled for
511unicast packets.
512When the option is more than once, it will be disabled for both
513unicast and multicast packets.
514.It Fl Y
515Same as
516.Fl y ,
517but with old packet format based on 03 draft.
518This option is present for backward compatibility.
519.Fl s
520has no effect if
521.Fl y
522is specified.
523.It Fl y
524Generate ICMPv6 Node Information DNS Name query, rather than echo-request.
525.Fl s
526has no effect if
527.Fl y
528is specified.
529.It Ar IPv6-hops
530IPv6 addresses for intermediate nodes,
531which will be put into type 0 routing header.
532.It Ar IPv6-host
533IPv6 address of the final destination node.
534.El
535.Ss Experimental options only for IPv6 target
536.Bl -tag -width indent
537.It Fl E
538Enables transport-mode IPsec encapsulated security payload.
539.It Fl Z
540Enables transport-mode IPsec authentication header.
541.El
542.Pp
543When using
544.Nm
545for fault isolation, it should first be run on the local host, to verify
546that the local network interface is up and running.
547Then, hosts and gateways further and further away should be
548.Dq pinged .
549Round-trip times and packet loss statistics are computed.
550If duplicate packets are received, they are not included in the packet
551loss calculation, although the round trip time of these packets is used
552in calculating the round-trip time statistics.
553When the specified number of packets have been sent
554(and received)
555or if the program is terminated with a
556.Dv SIGINT ,
557a brief summary is displayed, showing the number of packets sent and
558received, and the minimum, mean, maximum, and standard deviation of
559the round-trip times.
560.Pp
561If
562.Nm
563receives a
564.Dv SIGINFO
565(see the
566.Cm status
567argument for
568.Xr stty 1 )
569signal, the current number of packets sent and received, and the
570minimum, mean, maximum, and standard deviation of the round-trip times
571will be written to the standard output.
572.Pp
573This program is intended for use in network testing, measurement and
574management.
575Because of the load it can impose on the network, it is unwise to use
576.Nm
577during normal operations or from automated scripts.
578.Sh ICMP PACKET DETAILS
579An IP header without options is 20 bytes.
580An
581ICMP
582ECHO_REQUEST
583packet contains an additional 8 bytes worth of
584ICMP
585header followed by an arbitrary amount of data.
586When a
587.Ar packetsize
588is given, this indicated the size of this extra piece of data
589(the default is 56).
590Thus the amount of data received inside of an IP packet of type
591ICMP
592ECHO_REPLY
593will always be 8 bytes more than the requested data space
594(the
595ICMP
596header).
597.Pp
598If the data space is at least eight bytes large,
599.Nm
600uses the first eight bytes of this space to include a timestamp which
601it uses in the computation of round trip times.
602If less than eight bytes of pad are specified, no round trip times are
603given.
604.Sh DUPLICATE AND DAMAGED PACKETS
605The
606.Nm
607utility will report duplicate and damaged packets.
608Duplicate packets should never occur when pinging a unicast address,
609and seem to be caused by
610inappropriate link-level retransmissions.
611Duplicates may occur in many situations and are rarely
612(if ever)
613a good sign, although the presence of low levels of duplicates may not
614always be cause for alarm.
615Duplicates are expected when pinging a broadcast or multicast address,
616since they are not really duplicates but replies from different hosts
617to the same request.
618.Pp
619Damaged packets are obviously serious cause for alarm and often
620indicate broken hardware somewhere in the
621.Nm
622packet's path (in the network or in the hosts).
623.Sh TRYING DIFFERENT DATA PATTERNS
624The
625(inter)network
626layer should never treat packets differently depending on the data
627contained in the data portion.
628Unfortunately, data-dependent problems have been known to sneak into
629networks and remain undetected for long periods of time.
630In many cases the particular pattern that will have problems is something
631that does not have sufficient
632.Dq transitions ,
633such as all ones or all zeros, or a pattern right at the edge, such as
634almost all zeros.
635It is not
636necessarily enough to specify a data pattern of all zeros (for example)
637on the command line because the pattern that is of interest is
638at the data link level, and the relationship between what you type and
639what the controllers transmit can be complicated.
640.Pp
641This means that if you have a data-dependent problem you will probably
642have to do a lot of testing to find it.
643If you are lucky, you may manage to find a file that either
644cannot
645be sent across your network or that takes much longer to transfer than
646other similar length files.
647You can then examine this file for repeated patterns that you can test
648using the
649.Fl p
650option of
651.Nm .
652.Sh IPv4 TTL DETAILS
653The
654TTL
655value of an IP packet represents the maximum number of IP routers
656that the packet can go through before being thrown away.
657In current practice you can expect each router in the Internet to decrement
658the
659TTL
660field by exactly one.
661.Pp
662The
663TCP/IP
664specification recommends setting the
665TTL
666field for
667IP
668packets to 64.
669.Pp
670The maximum possible value of this field is 255, and some
671.Ux
672systems set
673the
674TTL
675field of
676ICMP ECHO_REQUEST
677packets to 255.
678This is why you will find you can
679.Dq ping
680some hosts, but not reach them with
681.Xr telnet 1
682or
683.Xr ftp 1 .
684.Pp
685In normal operation
686.Nm
687prints the ttl value from the packet it receives.
688When a remote system receives a ping packet, it can do one of three things
689with the
690TTL
691field in its response:
692.Bl -bullet
693.It
694Not change it; this is what
695.Bx
696systems did before the
697.Bx 4.3 tahoe
698release.
699In this case the
700TTL
701value in the received packet will be 255 minus the
702number of routers in the round-trip path.
703.It
704Set it to 64; this is what current
705.Fx
706systems do.
707In this case the
708TTL
709value in the received packet will be 64 minus the
710number of routers in the path
711.Em from
712the remote system
713.Em to
714the
715.Nm Ns Em ing
716host.
717.It
718Set it to some other value.
719Some machines use the same value for
720ICMP
721packets that they use for
722TCP
723packets, for example either 30 or 60.
724Others may use completely wild values.
725.El
726.Sh EXIT STATUS
727The
728.Nm
729utility exits with one of the following values:
730.Bl -tag -width indent
731.It 0
732At least one response was heard from the specified
733.Ar host .
734.It 2
735The transmission was successful but no responses were received.
736.It any other value
737An error occurred.
738.El
739.Sh EXAMPLES
740The following will send ICMPv6 echo request to
741.Li dst.example.com .
742.Bd -literal -offset indent
743ping -6 -n dst.example.com
744.Ed
745.Pp
746The following will probe hostnames for all nodes on the network link attached to
747.Li wi0
748interface.
749The address
750.Li ff02::1
751is named the link-local all-node multicast address, and the packet would
752reach every node on the network link.
753.Bd -literal -offset indent
754ping -6 -y ff02::1%wi0
755.Ed
756.Pp
757The following will probe addresses assigned to the destination node,
758.Li dst.example.com .
759.Bd -literal -offset indent
760ping -6 -k agl dst.example.com
761.Ed
762.Sh SEE ALSO
763.Xr netstat 1 ,
764.Xr icmp 4 ,
765.Xr icmp6 4 ,
766.Xr inet6 4 ,
767.Xr ip6 4 ,
768.Xr ifconfig 8 ,
769.Xr routed 8 ,
770.Xr traceroute 8 ,
771.Xr traceroute6 8
772.Rs
773.%A A. Conta
774.%A S. Deering
775.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"
776.%N RFC 2463
777.%D December 1998
778.Re
779.Rs
780.%A Matt Crawford
781.%T "IPv6 Node Information Queries"
782.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt
783.%D May 2002
784.%O work in progress material
785.Re
786.Sh HISTORY
787The
788.Nm
789utility appeared in
790.Bx 4.3 .
791The
792.Nm ping6
793utility with IPv6 support first appeared in the WIDE Hydrangea IPv6
794protocol stack kit.
795.Pp
796IPv6 and IPsec support based on the KAME Project
797.Pq Pa https://www.kame.net/
798stack was initially integrated into
799.Fx 4.0 .
800.Pp
801The
802.Nm ping6
803utility was merged to
804.Nm
805in Google Summer of Code 2019.
806.Sh AUTHORS
807The original
808.Nm
809utility was written by
810.An Mike Muuss
811while at the US Army Ballistics
812Research Laboratory.
813.Sh BUGS
814Many Hosts and Gateways ignore the IPv4
815RECORD_ROUTE
816option.
817.Pp
818The maximum IP header length is too small for options like
819RECORD_ROUTE
820to be completely useful.
821.No There Ap s
822not much that can be done about this, however.
823.Pp
824Flood pinging is not recommended in general, and flood pinging the
825broadcast address should only be done under very controlled conditions.
826.Pp
827The
828.Fl v
829option is not worth much on busy hosts.
830