1.\" Copyright (c) 1985, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)ping.8 8.2 (Berkeley) 12/11/93 29.\" $FreeBSD$ 30.\" 31.Dd August 22, 2019 32.Dt PING 8 33.Os 34.Sh NAME 35.Nm ping 36.Nd send 37.Tn ICMP ECHO_REQUEST 38packets to network hosts 39.Sh SYNOPSIS 40.Nm 41.Op Fl AaDdfHnoQqRrv 42.Op Fl c Ar count 43.Op Fl G Ar sweepmaxsize 44.Op Fl g Ar sweepminsize 45.Op Fl h Ar sweepincrsize 46.Op Fl i Ar wait 47.Op Fl l Ar preload 48.Op Fl M Cm mask | time 49.Op Fl m Ar ttl 50.Op Fl P Ar policy 51.Op Fl p Ar pattern 52.Op Fl S Ar src_addr 53.Op Fl s Ar packetsize 54.Op Fl t Ar timeout 55.Op Fl W Ar waittime 56.Op Fl z Ar tos 57.Ar host 58.Nm 59.Op Fl AaDdfHLnoQqRrv 60.Op Fl c Ar count 61.Op Fl I Ar iface 62.Op Fl i Ar wait 63.Op Fl l Ar preload 64.Op Fl M Cm mask | time 65.Op Fl m Ar ttl 66.Op Fl P Ar policy 67.Op Fl p Ar pattern 68.Op Fl S Ar src_addr 69.Op Fl s Ar packetsize 70.Op Fl T Ar ttl 71.Op Fl t Ar timeout 72.Op Fl W Ar waittime 73.Op Fl z Ar tos 74.Ar mcast-group 75.Sh DESCRIPTION 76The 77.Nm 78utility uses the 79.Tn ICMP 80.No protocol Ap s mandatory 81.Tn ECHO_REQUEST 82datagram to elicit an 83.Tn ICMP ECHO_RESPONSE 84from a host or gateway. 85.Tn ECHO_REQUEST 86datagrams 87.Pq Dq pings 88have an IP and 89.Tn ICMP 90header, followed by a 91.Dq struct timeval 92and then an arbitrary number of 93.Dq pad 94bytes used to fill out the packet. 95The options are as follows: 96.Bl -tag -width indent 97.It Fl A 98Audible. 99Output a bell 100.Tn ( ASCII 1010x07) 102character when no packet is received before the next packet 103is transmitted. 104To cater for round-trip times that are longer than the interval 105between transmissions, further missing packets cause a bell only 106if the maximum number of unreceived packets has increased. 107.It Fl a 108Audible. 109Include a bell 110.Tn ( ASCII 1110x07) 112character in the output when any packet is received. 113This option is ignored 114if other format options are present. 115.It Fl c Ar count 116Stop after sending 117(and receiving) 118.Ar count 119.Tn ECHO_RESPONSE 120packets. 121If this option is not specified, 122.Nm 123will operate until interrupted. 124If this option is specified in conjunction with ping sweeps, 125each sweep will consist of 126.Ar count 127packets. 128.It Fl D 129Set the Don't Fragment bit. 130.It Fl d 131Set the 132.Dv SO_DEBUG 133option on the socket being used. 134.It Fl f 135Flood ping. 136Outputs packets as fast as they come back or one hundred times per second, 137whichever is more. 138For every 139.Tn ECHO_REQUEST 140sent a period 141.Dq .\& 142is printed, while for every 143.Tn ECHO_REPLY 144received a backspace is printed. 145This provides a rapid display of how many packets are being dropped. 146Only the super-user may use this option. 147.Bf -emphasis 148This can be very hard on a network and should be used with caution. 149.Ef 150.It Fl G Ar sweepmaxsize 151Specify the maximum size of 152.Tn ICMP 153payload when sending sweeping pings. 154This option is required for ping sweeps. 155.It Fl g Ar sweepminsize 156Specify the size of 157.Tn ICMP 158payload to start with when sending sweeping pings. 159The default value is 0. 160.It Fl H 161Hostname output. 162Try to do a reverse DNS lookup when displaying addresses. 163This is the opposite of the 164.Fl n 165option. 166.It Fl h Ar sweepincrsize 167Specify the number of bytes to increment the size of 168.Tn ICMP 169payload after 170each sweep when sending sweeping pings. 171The default value is 1. 172.It Fl I Ar iface 173Source multicast packets with the given interface address. 174This flag only applies if the ping destination is a multicast address. 175.It Fl i Ar wait 176Wait 177.Ar wait 178seconds 179.Em between sending each packet . 180The default is to wait for one second between each packet. 181The wait time may be fractional, but only the super-user may specify 182values less than 1 second. 183This option is incompatible with the 184.Fl f 185option. 186.It Fl L 187Suppress loopback of multicast packets. 188This flag only applies if the ping destination is a multicast address. 189.It Fl l Ar preload 190If 191.Ar preload 192is specified, 193.Nm 194sends that many packets as fast as possible before falling into its normal 195mode of behavior. 196Only the super-user may use this option. 197.It Fl M Cm mask | time 198Use 199.Dv ICMP_MASKREQ 200or 201.Dv ICMP_TSTAMP 202instead of 203.Dv ICMP_ECHO . 204For 205.Cm mask , 206print the netmask of the remote machine. 207Set the 208.Va net.inet.icmp.maskrepl 209MIB variable to enable 210.Dv ICMP_MASKREPLY 211and 212.Va net.inet.icmp.maskfake 213if you want to override the netmask in the response. 214For 215.Cm time , 216print the origination, reception and transmission timestamps. 217Set the 218.Va net.inet.icmp.tstamprepl 219MIB variable to enable or disable 220.Dv ICMP_TSTAMPREPLY . 221.It Fl m Ar ttl 222Set the IP Time To Live for outgoing packets. 223If not specified, the kernel uses the value of the 224.Va net.inet.ip.ttl 225MIB variable. 226.It Fl n 227Numeric output only. 228No attempt will be made to lookup symbolic names for host addresses. 229This is the opposite of 230.Fl H , 231and it is the default behavior. 232.It Fl o 233Exit successfully after receiving one reply packet. 234.It Fl P Ar policy 235.Ar policy 236specifies IPsec policy for the ping session. 237For details please refer to 238.Xr ipsec 4 239and 240.Xr ipsec_set_policy 3 . 241.It Fl p Ar pattern 242You may specify up to 16 243.Dq pad 244bytes to fill out the packet you send. 245This is useful for diagnosing data-dependent problems in a network. 246For example, 247.Dq Li \-p ff 248will cause the sent packet to be filled with all 249ones. 250.It Fl Q 251Somewhat quiet output. 252.No Don Ap t 253display ICMP error messages that are in response to our query messages. 254Originally, the 255.Fl v 256flag was required to display such errors, but 257.Fl v 258displays all ICMP error messages. 259On a busy machine, this output can be overbearing. 260Without the 261.Fl Q 262flag, 263.Nm 264prints out any ICMP error messages caused by its own ECHO_REQUEST 265messages. 266.It Fl q 267Quiet output. 268Nothing is displayed except the summary lines at startup time and 269when finished. 270.It Fl R 271Record route. 272Includes the 273.Tn RECORD_ROUTE 274option in the 275.Tn ECHO_REQUEST 276packet and displays 277the route buffer on returned packets. 278Note that the IP header is only large enough for nine such routes; 279the 280.Xr traceroute 8 281command is usually better at determining the route packets take to a 282particular destination. 283If more routes come back than should, such as due to an illegal spoofed 284packet, ping will print the route list and then truncate it at the correct 285spot. 286Many hosts ignore or discard the 287.Tn RECORD_ROUTE 288option. 289.It Fl r 290Bypass the normal routing tables and send directly to a host on an attached 291network. 292If the host is not on a directly-attached network, an error is returned. 293This option can be used to ping a local host through an interface 294that has no route through it 295(e.g., after the interface was dropped by 296.Xr routed 8 ) . 297.It Fl S Ar src_addr 298Use the following IP address as the source address in outgoing packets. 299On hosts with more than one IP address, this option can be used to 300force the source address to be something other than the IP address 301of the interface the probe packet is sent on. 302If the IP address 303is not one of this machine's interface addresses, an error is 304returned and nothing is sent. 305.It Fl s Ar packetsize 306Specify the number of data bytes to be sent. 307The default is 56, which translates into 64 308.Tn ICMP 309data bytes when combined 310with the 8 bytes of 311.Tn ICMP 312header data. 313Only the super-user may specify values more than default. 314This option cannot be used with ping sweeps. 315.It Fl T Ar ttl 316Set the IP Time To Live for multicasted packets. 317This flag only applies if the ping destination is a multicast address. 318.It Fl t Ar timeout 319Specify a timeout, in seconds, before ping exits regardless of how 320many packets have been received. 321.It Fl v 322Verbose output. 323.Tn ICMP 324packets other than 325.Tn ECHO_RESPONSE 326that are received are listed. 327.It Fl W Ar waittime 328Time in milliseconds to wait for a reply for each packet sent. 329If a reply arrives later, the packet is not printed as replied, but 330considered as replied when calculating statistics. 331.It Fl z Ar tos 332Use the specified type of service. 333.El 334.Pp 335When using 336.Nm 337for fault isolation, it should first be run on the local host, to verify 338that the local network interface is up and running. 339Then, hosts and gateways further and further away should be 340.Dq pinged . 341Round-trip times and packet loss statistics are computed. 342If duplicate packets are received, they are not included in the packet 343loss calculation, although the round trip time of these packets is used 344in calculating the round-trip time statistics. 345When the specified number of packets have been sent 346(and received) 347or if the program is terminated with a 348.Dv SIGINT , 349a brief summary is displayed, showing the number of packets sent and 350received, and the minimum, mean, maximum, and standard deviation of 351the round-trip times. 352.Pp 353If 354.Nm 355receives a 356.Dv SIGINFO 357(see the 358.Cm status 359argument for 360.Xr stty 1 ) 361signal, the current number of packets sent and received, and the 362minimum, mean, and maximum of the round-trip times will be written to 363the standard error output. 364.Pp 365This program is intended for use in network testing, measurement and 366management. 367Because of the load it can impose on the network, it is unwise to use 368.Nm 369during normal operations or from automated scripts. 370.Sh ICMP PACKET DETAILS 371An IP header without options is 20 bytes. 372An 373.Tn ICMP 374.Tn ECHO_REQUEST 375packet contains an additional 8 bytes worth of 376.Tn ICMP 377header followed by an arbitrary amount of data. 378When a 379.Ar packetsize 380is given, this indicated the size of this extra piece of data 381(the default is 56). 382Thus the amount of data received inside of an IP packet of type 383.Tn ICMP 384.Tn ECHO_REPLY 385will always be 8 bytes more than the requested data space 386(the 387.Tn ICMP 388header). 389.Pp 390If the data space is at least eight bytes large, 391.Nm 392uses the first eight bytes of this space to include a timestamp which 393it uses in the computation of round trip times. 394If less than eight bytes of pad are specified, no round trip times are 395given. 396.Sh DUPLICATE AND DAMAGED PACKETS 397The 398.Nm 399utility will report duplicate and damaged packets. 400Duplicate packets should never occur when pinging a unicast address, 401and seem to be caused by 402inappropriate link-level retransmissions. 403Duplicates may occur in many situations and are rarely 404(if ever) 405a good sign, although the presence of low levels of duplicates may not 406always be cause for alarm. 407Duplicates are expected when pinging a broadcast or multicast address, 408since they are not really duplicates but replies from different hosts 409to the same request. 410.Pp 411Damaged packets are obviously serious cause for alarm and often 412indicate broken hardware somewhere in the 413.Nm 414packet's path (in the network or in the hosts). 415.Sh TRYING DIFFERENT DATA PATTERNS 416The 417(inter)network 418layer should never treat packets differently depending on the data 419contained in the data portion. 420Unfortunately, data-dependent problems have been known to sneak into 421networks and remain undetected for long periods of time. 422In many cases the particular pattern that will have problems is something 423that does not have sufficient 424.Dq transitions , 425such as all ones or all zeros, or a pattern right at the edge, such as 426almost all zeros. 427It is not 428necessarily enough to specify a data pattern of all zeros (for example) 429on the command line because the pattern that is of interest is 430at the data link level, and the relationship between what you type and 431what the controllers transmit can be complicated. 432.Pp 433This means that if you have a data-dependent problem you will probably 434have to do a lot of testing to find it. 435If you are lucky, you may manage to find a file that either 436cannot 437be sent across your network or that takes much longer to transfer than 438other similar length files. 439You can then examine this file for repeated patterns that you can test 440using the 441.Fl p 442option of 443.Nm . 444.Sh TTL DETAILS 445The 446.Tn TTL 447value of an IP packet represents the maximum number of IP routers 448that the packet can go through before being thrown away. 449In current practice you can expect each router in the Internet to decrement 450the 451.Tn TTL 452field by exactly one. 453.Pp 454The 455.Tn TCP/IP 456specification recommends setting the 457.Tn TTL 458field for 459.Tn IP 460packets to 64, but many systems use smaller values 461.No ( Bx 4.3 462uses 30, 463.Bx 4.2 464used 15). 465.Pp 466The maximum possible value of this field is 255, and most 467.Ux 468systems set 469the 470.Tn TTL 471field of 472.Tn ICMP ECHO_REQUEST 473packets to 255. 474This is why you will find you can 475.Dq ping 476some hosts, but not reach them with 477.Xr telnet 1 478or 479.Xr ftp 1 . 480.Pp 481In normal operation 482.Nm 483prints the ttl value from the packet it receives. 484When a remote system receives a ping packet, it can do one of three things 485with the 486.Tn TTL 487field in its response: 488.Bl -bullet 489.It 490Not change it; this is what 491.Bx 492systems did before the 493.Bx 4.3 tahoe 494release. 495In this case the 496.Tn TTL 497value in the received packet will be 255 minus the 498number of routers in the round-trip path. 499.It 500Set it to 255; this is what current 501.Bx 502systems do. 503In this case the 504.Tn TTL 505value in the received packet will be 255 minus the 506number of routers in the path 507.Em from 508the remote system 509.Em to 510the 511.Nm Ns Em ing 512host. 513.It 514Set it to some other value. 515Some machines use the same value for 516.Tn ICMP 517packets that they use for 518.Tn TCP 519packets, for example either 30 or 60. 520Others may use completely wild values. 521.El 522.Sh EXIT STATUS 523The 524.Nm 525utility exits with one of the following values: 526.Bl -tag -width indent 527.It 0 528At least one response was heard from the specified 529.Ar host . 530.It 2 531The transmission was successful but no responses were received. 532.It any other value 533An error occurred. 534These values are defined in 535.In sysexits.h . 536.El 537.Sh SEE ALSO 538.Xr netstat 1 , 539.Xr icmp 4 , 540.Xr ifconfig 8 , 541.Xr routed 8 , 542.Xr traceroute 8 543.Sh HISTORY 544The 545.Nm 546utility appeared in 547.Bx 4.3 . 548.Sh AUTHORS 549The original 550.Nm 551utility was written by 552.An Mike Muuss 553while at the US Army Ballistics 554Research Laboratory. 555.Sh BUGS 556Many Hosts and Gateways ignore the 557.Tn RECORD_ROUTE 558option. 559.Pp 560The maximum IP header length is too small for options like 561.Tn RECORD_ROUTE 562to be completely useful. 563.No There Ap s 564not much that can be done about this, however. 565.Pp 566Flood pinging is not recommended in general, and flood pinging the 567broadcast address should only be done under very controlled conditions. 568.Pp 569The 570.Fl v 571option is not worth much on busy hosts. 572