xref: /freebsd/sbin/ping/ping.8 (revision bd66c1b43e33540205dbc1187c2f2a15c58b57ba)
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28.Dd October 15, 2024
29.Dt PING 8
30.Os
31.Sh NAME
32.Nm ping
33.Nd send
34ICMP
35or
36ICMPv6 ECHO_REQUEST
37packets to network hosts
38.Sh SYNOPSIS
39.Nm
40.Op Fl 4AaDdfHnoQqRrv
41.Op Fl .\& Ns Ar chars
42.Op Fl C Ar pcp
43.Op Fl c Ar count
44.Op Fl G Ar sweepmaxsize
45.Op Fl g Ar sweepminsize
46.Op Fl h Ar sweepincrsize
47.Op Fl i Ar wait
48.Op Fl l Ar preload
49.Op Fl M Cm mask | time
50.Op Fl m Ar ttl
51.Op Fl P Ar policy
52.Op Fl p Ar pattern
53.Op Fl S Ar src_addr
54.Op Fl s Ar packetsize
55.Op Fl t Ar timeout
56.Op Fl W Ar waittime
57.Op Fl z Ar tos
58.Ar IPv4-host
59.Nm
60.Op Fl 4AaDdfHLnoQqRrv
61.Op Fl .\& Ns Ar chars
62.Op Fl C Ar pcp
63.Op Fl c Ar count
64.Op Fl I Ar iface
65.Op Fl i Ar wait
66.Op Fl l Ar preload
67.Op Fl M Cm mask | time
68.Op Fl m Ar ttl
69.Op Fl P Ar policy
70.Op Fl p Ar pattern
71.Op Fl S Ar src_addr
72.Op Fl s Ar packetsize
73.Op Fl T Ar ttl
74.Op Fl t Ar timeout
75.Op Fl W Ar waittime
76.Op Fl z Ar tos
77.Ar IPv4-mcast-group
78.Nm
79.Op Fl 6AaDdEfHNnOoquvYyZ
80.Op Fl .\& Ns Ar chars
81.Op Fl b Ar bufsiz
82.Op Fl C Ar pcp
83.Op Fl c Ar count
84.Op Fl e Ar gateway
85.Op Fl I Ar interface
86.Op Fl i Ar wait
87.Op Fl k Ar addrtype
88.Op Fl l Ar preload
89.Op Fl m Ar hoplimit
90.Op Fl P Ar policy
91.Op Fl p Ar pattern
92.Op Fl S Ar sourceaddr
93.Op Fl s Ar packetsize
94.Op Fl t Ar timeout
95.Op Fl W Ar waittime
96.Op Ar IPv6-hops ...
97.Ar IPv6-host
98.Sh DESCRIPTION
99The
100.Nm
101utility invoked with an IPv4 target
102.Ar ( IPv4-host
103or
104.Ar IPv4-mcast-group )
105uses the
106ICMP
107.No protocol Ap s mandatory
108ECHO_REQUEST
109datagram to elicit an
110ICMP ECHO_RESPONSE
111from a host or gateway.
112ECHO_REQUEST
113datagrams
114.Pq Dq pings
115have an IP and
116ICMP
117header, followed by a
118.Dq struct timeval
119and then an arbitrary number of
120.Dq pad
121bytes used to fill out the packet.
122.Pp
123When invoked with an IPv6 target
124.Ar ( IPv6-host ) ,
125it uses the
126ICMPv6
127protocol's mandatory
128ICMP6_ECHO_REQUEST
129datagram to elicit an
130ICMP6_ECHO_REPLY.
131ICMP6_ECHO_REQUEST
132datagrams have an IPv6 header and
133ICMPv6
134header formatted as documented in RFC 2463.
135.Pp
136When invoked with a hostname, the version to which the target is resolved first
137is used.
138In that case, the options and arguments used must be valid for the specific IP
139version, otherwise
140.Nm
141exits with an error.
142If the target is resolved to both IPv4 and IPv6, the specific IP version can be
143requested by
144.Fl 4
145or
146.Fl 6
147options, respectively.
148For backwards-compatibility, ICMPv6 can also be selected by invoking the binary
149as
150.Nm ping6 .
151.Ss Options common to both IPv4 and IPv6 targets
152.Bl -tag -width indent
153.It Fl .\& Ns Ar chars
154By default, for every
155ECHO_REQUEST
156sent, a period
157.Dq .\&
158is printed, while for every
159ECHO_REPLY
160received, a backspace is printed.
161This option takes an optional string argument listing characters
162that will be printed one by one in the provided order
163instead of the default period.
164.Pp
165Example usage:
166.Bd -literal -offset indent
167ping -.0123456789 freebsd.org
168.Ed
169.It Fl A
170Audible.
171Output a bell
172(ASCII
1730x07)
174character when no packet is received before the next packet
175is transmitted.
176To cater for round-trip times that are longer than the interval
177between transmissions, further missing packets cause a bell only
178if the maximum number of unreceived packets has increased.
179.It Fl a
180Audible.
181Include a bell
182(ASCII
1830x07)
184character in the output when any packet is received.
185.It Fl C Ar pcp
186Add an 802.1p Ethernet Priority Code Point when sending a packet.
1870..7 uses that specific PCP, -1 uses the interface default PCP (or none).
188.It Fl c Ar count
189Stop after sending
190(and receiving)
191.Ar count
192ECHO_RESPONSE
193packets.
194If this option is not specified,
195.Nm
196will operate until interrupted.
197.Pp
198For an IPv4 target, if this option is specified in conjunction with ping sweeps,
199each sweep will consist of
200.Ar count
201packets.
202.It Fl D
203Disable fragmentation.
204.It Fl d
205Set the
206.Dv SO_DEBUG
207option on the socket being used.
208.It Fl f
209Flood ping.
210Outputs packets as fast as they come back or one hundred times per second,
211whichever is more.
212Implies
213.Fl .\&
214to print a period for every
215ECHO_REQUEST
216sent and a backspace for every
217ECHO_REPLY
218received.
219This provides a rapid display of how many packets are being dropped.
220Only the super-user may use this option.
221.Bf -emphasis
222This can be very hard on a network and should be used with caution.
223.Ef
224.It Fl H
225Hostname output.
226Try to do a reverse DNS lookup when displaying addresses.
227This is the opposite of the
228.Fl n
229option.
230.It Fl I Ar iface
231For an IPv4 target,
232.Ar iface
233is an IP address indentifying an interface from which the packets will be sent.
234This flag applies only if the ping target is a multicast address.
235.Pp
236For an IPv6 target,
237.Ar iface
238is a name of an interface (e.g., `em0') from which the packets will be sent.
239This flag applies if the ping target is a multicast address, or
240link-local/site-local unicast address.
241.It Fl i Ar wait
242Wait
243.Ar wait
244seconds
245.Em between sending each packet .
246The default is to wait for one second between each packet.
247The wait time may be fractional, but only the super-user may specify
248values less than 1 second.
249This option is incompatible with the
250.Fl f
251option.
252.It Fl l Ar preload
253If
254.Ar preload
255is specified,
256.Nm
257sends that many packets as fast as possible before falling into its normal
258mode of behavior.
259Only the super-user may use this option.
260.It Fl m Ar ttl
261For an IPv4 target, set the IP Time To Live for outgoing packets.
262If not specified, the kernel uses the value of the
263.Va net.inet.ip.ttl
264MIB variable.
265.Pp
266For an IPv6 target, set the IPv6 hoplimit.
267.It Fl n
268Numeric output only.
269No attempt will be made to lookup symbolic names for host addresses.
270This is the opposite of
271.Fl H ,
272and it is the default behavior.
273.It Fl o
274Exit successfully after receiving one reply packet.
275.It Fl P Ar policy
276.Ar policy
277specifies IPsec policy for the ping session.
278For details please refer to
279.Xr ipsec 4
280and
281.Xr ipsec_set_policy 3 .
282.It Fl p Ar pattern
283You may specify up to 16
284.Dq pad
285bytes to fill out the packet you send.
286This is useful for diagnosing data-dependent problems in a network.
287For example,
288.Dq Li \-p ff
289will cause the sent packet to be filled with all
290ones.
291.It Fl q
292Quiet output.
293Nothing is displayed except the summary lines at startup time and
294when finished.
295.It Fl S Ar src_addr
296Use the following IP address as the source address in outgoing packets.
297On hosts with more than one IP address, this option can be used to
298force the source address to be something other than the IP address
299of the interface the probe packet is sent on.
300.Pp
301For IPv4, if the IP address is not one of this machine's interface
302addresses, an error is returned and nothing is sent.
303.Pp
304For IPv6, the source address must be one of the unicast addresses of
305the sending node, and must be numeric.
306.It Fl s Ar packetsize
307Specify the number of data bytes to be sent.
308The default is 56, which translates into 64
309ICMP
310data bytes when combined
311with the 8 bytes of
312ICMP
313header data.
314.Pp
315This option cannot be used with ping sweeps.
316.Pp
317For IPv6, you may need to specify
318.Fl b
319as well to extend socket buffer size.
320.It Fl t Ar timeout
321Specify a timeout, in seconds, before ping exits regardless of how
322many packets have been received.
323.It Fl v
324Verbose output.
325ICMP
326packets other than
327ECHO_RESPONSE
328that are received are listed.
329.It Fl W Ar waittime
330Time in milliseconds to wait for a reply for each packet sent.
331If a reply arrives later, the packet is not printed as replied, but
332considered as replied when calculating statistics.
333.El
334.Ss Options only for IPv4 targets
335.Bl -tag -width indent
336.It Fl 4
337Use IPv4 regardless of how the target is resolved.
338.It Fl G Ar sweepmaxsize
339Specify the maximum size of
340ICMP
341payload when sending sweeping pings.
342This option is required for ping sweeps.
343.It Fl g Ar sweepminsize
344Specify the size of
345ICMP
346payload to start with when sending sweeping pings.
347The default value is 0.
348.It Fl h Ar sweepincrsize
349Specify the number of bytes to increment the size of
350ICMP
351payload after
352each sweep when sending sweeping pings.
353The default value is 1.
354.It Fl L
355Suppress loopback of multicast packets.
356This flag only applies if the ping destination is a multicast address.
357.It Fl M Cm mask | time
358Use
359.Dv ICMP_MASKREQ
360or
361.Dv ICMP_TSTAMP
362instead of
363.Dv ICMP_ECHO .
364For
365.Cm mask ,
366print the netmask of the remote machine.
367Set the
368.Va net.inet.icmp.maskrepl
369MIB variable to enable
370.Dv ICMP_MASKREPLY
371and
372.Va net.inet.icmp.maskfake
373if you want to override the netmask in the response.
374For
375.Cm time ,
376print the origination, reception and transmission timestamps.
377Set the
378.Va net.inet.icmp.tstamprepl
379MIB variable to enable or disable
380.Dv ICMP_TSTAMPREPLY .
381.It Fl Q
382Somewhat quiet output.
383.No Don Ap t
384display ICMP error messages that are in response to our query messages.
385Originally, the
386.Fl v
387flag was required to display such errors, but
388.Fl v
389displays all ICMP error messages.
390On a busy machine, this output can be overbearing.
391Without the
392.Fl Q
393flag,
394.Nm
395prints out any ICMP error messages caused by its own ECHO_REQUEST
396messages.
397.It Fl R
398Record route.
399Includes the
400RECORD_ROUTE
401option in the
402ECHO_REQUEST
403packet and displays
404the route buffer on returned packets.
405Note that the IP header is only large enough for nine such routes;
406the
407.Xr traceroute 8
408command is usually better at determining the route packets take to a
409particular destination.
410If more routes come back than should, such as due to an illegal spoofed
411packet, ping will print the route list and then truncate it at the correct
412spot.
413Many hosts ignore or discard the
414RECORD_ROUTE
415option.
416.It Fl r
417Bypass the normal routing tables and send directly to a host on an attached
418network.
419If the host is not on a directly-attached network, an error is returned.
420This option can be used to ping a local host through an interface
421that has no route through it
422(e.g., after the interface was dropped by
423.Xr routed 8 ) .
424.It Fl T Ar ttl
425Set the IP Time To Live for multicasted packets.
426This flag only applies if the ping destination is a multicast address.
427.It Fl z Ar tos
428Use the specified type of service.
429.It Ar IPv4-host
430hostname or IPv4 address of the final destination node.
431.It Ar IPv4-mcast-group
432IPv4 multicast address of the final destination nodes.
433.El
434.Ss Options only for IPv6 targets
435.Bl -tag -width indent
436.It Fl 6
437Use IPv6 regardless of how the target is resolved.
438.It Fl b Ar bufsiz
439Set socket buffer size.
440.It Fl e Ar gateway
441Specifies to use
442.Ar gateway
443as the next hop to the destination.
444The gateway must be a neighbor of the sending node.
445.It Fl k Ar addrtype
446Generate ICMPv6 Node Information Node Addresses query, rather than echo-request.
447.Ar addrtype
448must be a string constructed of the following characters.
449.Bl -tag -width Ds -compact
450.It Ic a
451requests unicast addresses from all of the responder's interfaces.
452If the character is omitted,
453only those addresses which belong to the interface which has the
454responder's address are requests.
455.It Ic c
456requests responder's IPv4-compatible and IPv4-mapped addresses.
457.It Ic g
458requests responder's global-scope addresses.
459.It Ic s
460requests responder's site-local addresses.
461.It Ic l
462requests responder's link-local addresses.
463.It Ic A
464requests responder's anycast addresses.
465Without this character, the responder will return unicast addresses only.
466With this character, the responder will return anycast addresses only.
467Note that the specification does not specify how to get responder's
468anycast addresses.
469This is an experimental option.
470.El
471.It Fl N
472Probe node information multicast group address
473.Pq Li ff02::2:ffxx:xxxx .
474.Ar host
475must be string hostname of the target
476(must not be a numeric IPv6 address).
477Node information multicast group will be computed based on given
478.Ar host ,
479and will be used as the final destination.
480Since node information multicast group is a link-local multicast group,
481outgoing interface needs to be specified by
482.Fl I
483option.
484.Pp
485When specified twice, the address
486.Pq Li ff02::2:xxxx:xxxx
487is used instead.
488The former is in RFC 4620, the latter is in an old Internet Draft
489draft-ietf-ipngwg-icmp-name-lookup.
490Note that KAME-derived implementations including
491.Fx
492use the latter.
493.It Fl O
494Generate ICMPv6 Node Information supported query types query,
495rather than echo-request.
496.Fl s
497has no effect if
498.Fl O
499is specified.
500.It Fl u
501By default,
502.Nm
503asks the kernel to fragment packets to fit into the minimum IPv6 MTU.
504The
505.Fl u
506option
507will suppress the behavior in the following two levels:
508when the option is specified once, the behavior will be disabled for
509unicast packets.
510When the option is more than once, it will be disabled for both
511unicast and multicast packets.
512.It Fl Y
513Same as
514.Fl y ,
515but with old packet format based on 03 draft.
516This option is present for backward compatibility.
517.Fl s
518has no effect if
519.Fl y
520is specified.
521.It Fl y
522Generate ICMPv6 Node Information DNS Name query, rather than echo-request.
523.Fl s
524has no effect if
525.Fl y
526is specified.
527.It Ar IPv6-hops
528IPv6 addresses for intermediate nodes,
529which will be put into type 0 routing header.
530.It Ar IPv6-host
531IPv6 address of the final destination node.
532.El
533.Ss Experimental options only for IPv6 target
534.Bl -tag -width indent
535.It Fl E
536Enables transport-mode IPsec encapsulated security payload.
537.It Fl Z
538Enables transport-mode IPsec authentication header.
539.El
540.Pp
541When using
542.Nm
543for fault isolation, it should first be run on the local host, to verify
544that the local network interface is up and running.
545Then, hosts and gateways further and further away should be
546.Dq pinged .
547Round-trip times and packet loss statistics are computed.
548If duplicate packets are received, they are not included in the packet
549loss calculation, although the round trip time of these packets is used
550in calculating the round-trip time statistics.
551When the specified number of packets have been sent
552(and received)
553or if the program is terminated with a
554.Dv SIGINT ,
555a brief summary is displayed, showing the number of packets sent and
556received, and the minimum, mean, maximum, and standard deviation of
557the round-trip times.
558.Pp
559If
560.Nm
561receives a
562.Dv SIGINFO
563(see the
564.Cm status
565argument for
566.Xr stty 1 )
567signal, the current number of packets sent and received, and the
568minimum, mean, maximum, and standard deviation of the round-trip times
569will be written to the standard output.
570.Pp
571This program is intended for use in network testing, measurement and
572management.
573Because of the load it can impose on the network, it is unwise to use
574.Nm
575during normal operations or from automated scripts.
576.Sh ICMP PACKET DETAILS
577An IP header without options is 20 bytes.
578An
579ICMP
580ECHO_REQUEST
581packet contains an additional 8 bytes worth of
582ICMP
583header followed by an arbitrary amount of data.
584When a
585.Ar packetsize
586is given, this indicated the size of this extra piece of data
587(the default is 56).
588Thus the amount of data received inside of an IP packet of type
589ICMP
590ECHO_REPLY
591will always be 8 bytes more than the requested data space
592(the
593ICMP
594header).
595.Pp
596If the data space is at least eight bytes large,
597.Nm
598uses the first eight bytes of this space to include a timestamp which
599it uses in the computation of round trip times.
600If less than eight bytes of pad are specified, no round trip times are
601given.
602.Sh DUPLICATE AND DAMAGED PACKETS
603The
604.Nm
605utility will report duplicate and damaged packets.
606Duplicate packets should never occur when pinging a unicast address,
607and seem to be caused by
608inappropriate link-level retransmissions.
609Duplicates may occur in many situations and are rarely
610(if ever)
611a good sign, although the presence of low levels of duplicates may not
612always be cause for alarm.
613Duplicates are expected when pinging a broadcast or multicast address,
614since they are not really duplicates but replies from different hosts
615to the same request.
616.Pp
617Damaged packets are obviously serious cause for alarm and often
618indicate broken hardware somewhere in the
619.Nm
620packet's path (in the network or in the hosts).
621.Sh TRYING DIFFERENT DATA PATTERNS
622The
623(inter)network
624layer should never treat packets differently depending on the data
625contained in the data portion.
626Unfortunately, data-dependent problems have been known to sneak into
627networks and remain undetected for long periods of time.
628In many cases the particular pattern that will have problems is something
629that does not have sufficient
630.Dq transitions ,
631such as all ones or all zeros, or a pattern right at the edge, such as
632almost all zeros.
633It is not
634necessarily enough to specify a data pattern of all zeros (for example)
635on the command line because the pattern that is of interest is
636at the data link level, and the relationship between what you type and
637what the controllers transmit can be complicated.
638.Pp
639This means that if you have a data-dependent problem you will probably
640have to do a lot of testing to find it.
641If you are lucky, you may manage to find a file that either
642cannot
643be sent across your network or that takes much longer to transfer than
644other similar length files.
645You can then examine this file for repeated patterns that you can test
646using the
647.Fl p
648option of
649.Nm .
650.Sh IPv4 TTL DETAILS
651The
652TTL
653value of an IP packet represents the maximum number of IP routers
654that the packet can go through before being thrown away.
655In current practice you can expect each router in the Internet to decrement
656the
657TTL
658field by exactly one.
659.Pp
660The
661TCP/IP
662specification recommends setting the
663TTL
664field for
665IP
666packets to 64.
667.Pp
668The maximum possible value of this field is 255, and some
669.Ux
670systems set
671the
672TTL
673field of
674ICMP ECHO_REQUEST
675packets to 255.
676This is why you will find you can
677.Dq ping
678some hosts, but not reach them with
679.Xr telnet 1
680or
681.Xr ftp 1 .
682.Pp
683In normal operation
684.Nm
685prints the ttl value from the packet it receives.
686When a remote system receives a ping packet, it can do one of three things
687with the
688TTL
689field in its response:
690.Bl -bullet
691.It
692Not change it; this is what
693.Bx
694systems did before the
695.Bx 4.3 tahoe
696release.
697In this case the
698TTL
699value in the received packet will be 255 minus the
700number of routers in the round-trip path.
701.It
702Set it to 64; this is what current
703.Fx
704systems do.
705In this case the
706TTL
707value in the received packet will be 64 minus the
708number of routers in the path
709.Em from
710the remote system
711.Em to
712the
713.Nm Ns Em ing
714host.
715.It
716Set it to some other value.
717Some machines use the same value for
718ICMP
719packets that they use for
720TCP
721packets, for example either 30 or 60.
722Others may use completely wild values.
723.El
724.Sh EXIT STATUS
725The
726.Nm
727utility exits with one of the following values:
728.Bl -tag -width indent
729.It 0
730At least one response was heard from the specified
731.Ar host .
732.It 2
733The transmission was successful but no responses were received.
734.It any other value
735An error occurred.
736.El
737.Sh EXAMPLES
738The following will send ICMPv6 echo request to
739.Li dst.example.com .
740.Bd -literal -offset indent
741ping -6 -n dst.example.com
742.Ed
743.Pp
744The following will probe hostnames for all nodes on the network link attached to
745.Li wi0
746interface.
747The address
748.Li ff02::1
749is named the link-local all-node multicast address, and the packet would
750reach every node on the network link.
751.Bd -literal -offset indent
752ping -6 -y ff02::1%wi0
753.Ed
754.Pp
755The following will probe addresses assigned to the destination node,
756.Li dst.example.com .
757.Bd -literal -offset indent
758ping -6 -k agl dst.example.com
759.Ed
760.Sh SEE ALSO
761.Xr netstat 1 ,
762.Xr icmp 4 ,
763.Xr icmp6 4 ,
764.Xr inet6 4 ,
765.Xr ip6 4 ,
766.Xr ifconfig 8 ,
767.Xr routed 8 ,
768.Xr traceroute 8 ,
769.Xr traceroute6 8
770.Rs
771.%A A. Conta
772.%A S. Deering
773.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"
774.%N RFC 2463
775.%D December 1998
776.Re
777.Rs
778.%A Matt Crawford
779.%T "IPv6 Node Information Queries"
780.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt
781.%D May 2002
782.%O work in progress material
783.Re
784.Sh HISTORY
785The
786.Nm
787utility appeared in
788.Bx 4.3 .
789The
790.Nm ping6
791utility with IPv6 support first appeared in the WIDE Hydrangea IPv6
792protocol stack kit.
793.Pp
794IPv6 and IPsec support based on the KAME Project
795.Pq Pa https://www.kame.net/
796stack was initially integrated into
797.Fx 4.0 .
798.Pp
799The
800.Nm ping6
801utility was merged to
802.Nm
803in Google Summer of Code 2019.
804.Sh AUTHORS
805The original
806.Nm
807utility was written by
808.An Mike Muuss
809while at the US Army Ballistics
810Research Laboratory.
811.Sh BUGS
812Many Hosts and Gateways ignore the IPv4
813RECORD_ROUTE
814option.
815.Pp
816The maximum IP header length is too small for options like
817RECORD_ROUTE
818to be completely useful.
819.No There Ap s
820not much that can be done about this, however.
821.Pp
822Flood pinging is not recommended in general, and flood pinging the
823broadcast address should only be done under very controlled conditions.
824.Pp
825The
826.Fl v
827option is not worth much on busy hosts.
828