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 March 11, 2016 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 AaDdfnoQqRrv 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 AaDdfLnoQqRrv 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 Ar sweepincrsize 161Specify the number of bytes to increment the size of 162.Tn ICMP 163payload after 164each sweep when sending sweeping pings. 165The default value is 1. 166.It Fl I Ar iface 167Source multicast packets with the given interface address. 168This flag only applies if the ping destination is a multicast address. 169.It Fl i Ar wait 170Wait 171.Ar wait 172seconds 173.Em between sending each packet . 174The default is to wait for one second between each packet. 175The wait time may be fractional, but only the super-user may specify 176values less than 1 second. 177This option is incompatible with the 178.Fl f 179option. 180.It Fl L 181Suppress loopback of multicast packets. 182This flag only applies if the ping destination is a multicast address. 183.It Fl l Ar preload 184If 185.Ar preload 186is specified, 187.Nm 188sends that many packets as fast as possible before falling into its normal 189mode of behavior. 190Only the super-user may use this option. 191.It Fl M Cm mask | time 192Use 193.Dv ICMP_MASKREQ 194or 195.Dv ICMP_TSTAMP 196instead of 197.Dv ICMP_ECHO . 198For 199.Cm mask , 200print the netmask of the remote machine. 201Set the 202.Va net.inet.icmp.maskrepl 203MIB variable to enable 204.Dv ICMP_MASKREPLY 205and 206.Va net.inet.icmp.maskfake 207if you want to override the netmask in the response. 208For 209.Cm time , 210print the origination, reception and transmission timestamps. 211Set the 212.Va net.inet.icmp.tstamprepl 213MIB variable to enable or disable 214.Dv ICMP_TSTAMPREPLY . 215.It Fl m Ar ttl 216Set the IP Time To Live for outgoing packets. 217If not specified, the kernel uses the value of the 218.Va net.inet.ip.ttl 219MIB variable. 220.It Fl n 221Numeric output only. 222No attempt will be made to lookup symbolic names for host addresses. 223.It Fl o 224Exit successfully after receiving one reply packet. 225.It Fl P Ar policy 226.Ar policy 227specifies IPsec policy for the ping session. 228For details please refer to 229.Xr ipsec 4 230and 231.Xr ipsec_set_policy 3 . 232.It Fl p Ar pattern 233You may specify up to 16 234.Dq pad 235bytes to fill out the packet you send. 236This is useful for diagnosing data-dependent problems in a network. 237For example, 238.Dq Li \-p ff 239will cause the sent packet to be filled with all 240ones. 241.It Fl Q 242Somewhat quiet output. 243.No Don Ap t 244display ICMP error messages that are in response to our query messages. 245Originally, the 246.Fl v 247flag was required to display such errors, but 248.Fl v 249displays all ICMP error messages. 250On a busy machine, this output can be overbearing. 251Without the 252.Fl Q 253flag, 254.Nm 255prints out any ICMP error messages caused by its own ECHO_REQUEST 256messages. 257.It Fl q 258Quiet output. 259Nothing is displayed except the summary lines at startup time and 260when finished. 261.It Fl R 262Record route. 263Includes the 264.Tn RECORD_ROUTE 265option in the 266.Tn ECHO_REQUEST 267packet and displays 268the route buffer on returned packets. 269Note that the IP header is only large enough for nine such routes; 270the 271.Xr traceroute 8 272command is usually better at determining the route packets take to a 273particular destination. 274If more routes come back than should, such as due to an illegal spoofed 275packet, ping will print the route list and then truncate it at the correct 276spot. 277Many hosts ignore or discard the 278.Tn RECORD_ROUTE 279option. 280.It Fl r 281Bypass the normal routing tables and send directly to a host on an attached 282network. 283If the host is not on a directly-attached network, an error is returned. 284This option can be used to ping a local host through an interface 285that has no route through it 286(e.g., after the interface was dropped by 287.Xr routed 8 ) . 288.It Fl S Ar src_addr 289Use the following IP address as the source address in outgoing packets. 290On hosts with more than one IP address, this option can be used to 291force the source address to be something other than the IP address 292of the interface the probe packet is sent on. 293If the IP address 294is not one of this machine's interface addresses, an error is 295returned and nothing is sent. 296.It Fl s Ar packetsize 297Specify the number of data bytes to be sent. 298The default is 56, which translates into 64 299.Tn ICMP 300data bytes when combined 301with the 8 bytes of 302.Tn ICMP 303header data. 304Only the super-user may specify values more than default. 305This option cannot be used with ping sweeps. 306.It Fl T Ar ttl 307Set the IP Time To Live for multicasted packets. 308This flag only applies if the ping destination is a multicast address. 309.It Fl t Ar timeout 310Specify a timeout, in seconds, before ping exits regardless of how 311many packets have been received. 312.It Fl v 313Verbose output. 314.Tn ICMP 315packets other than 316.Tn ECHO_RESPONSE 317that are received are listed. 318.It Fl W Ar waittime 319Time in milliseconds to wait for a reply for each packet sent. 320If a reply arrives later, the packet is not printed as replied, but 321considered as replied when calculating statistics. 322.It Fl z Ar tos 323Use the specified type of service. 324.El 325.Pp 326When using 327.Nm 328for fault isolation, it should first be run on the local host, to verify 329that the local network interface is up and running. 330Then, hosts and gateways further and further away should be 331.Dq pinged . 332Round-trip times and packet loss statistics are computed. 333If duplicate packets are received, they are not included in the packet 334loss calculation, although the round trip time of these packets is used 335in calculating the round-trip time statistics. 336When the specified number of packets have been sent 337(and received) 338or if the program is terminated with a 339.Dv SIGINT , 340a brief summary is displayed, showing the number of packets sent and 341received, and the minimum, mean, maximum, and standard deviation of 342the round-trip times. 343.Pp 344If 345.Nm 346receives a 347.Dv SIGINFO 348(see the 349.Cm status 350argument for 351.Xr stty 1 ) 352signal, the current number of packets sent and received, and the 353minimum, mean, and maximum of the round-trip times will be written to 354the standard error output. 355.Pp 356This program is intended for use in network testing, measurement and 357management. 358Because of the load it can impose on the network, it is unwise to use 359.Nm 360during normal operations or from automated scripts. 361.Sh ICMP PACKET DETAILS 362An IP header without options is 20 bytes. 363An 364.Tn ICMP 365.Tn ECHO_REQUEST 366packet contains an additional 8 bytes worth of 367.Tn ICMP 368header followed by an arbitrary amount of data. 369When a 370.Ar packetsize 371is given, this indicated the size of this extra piece of data 372(the default is 56). 373Thus the amount of data received inside of an IP packet of type 374.Tn ICMP 375.Tn ECHO_REPLY 376will always be 8 bytes more than the requested data space 377(the 378.Tn ICMP 379header). 380.Pp 381If the data space is at least eight bytes large, 382.Nm 383uses the first eight bytes of this space to include a timestamp which 384it uses in the computation of round trip times. 385If less than eight bytes of pad are specified, no round trip times are 386given. 387.Sh DUPLICATE AND DAMAGED PACKETS 388The 389.Nm 390utility will report duplicate and damaged packets. 391Duplicate packets should never occur when pinging a unicast address, 392and seem to be caused by 393inappropriate link-level retransmissions. 394Duplicates may occur in many situations and are rarely 395(if ever) 396a good sign, although the presence of low levels of duplicates may not 397always be cause for alarm. 398Duplicates are expected when pinging a broadcast or multicast address, 399since they are not really duplicates but replies from different hosts 400to the same request. 401.Pp 402Damaged packets are obviously serious cause for alarm and often 403indicate broken hardware somewhere in the 404.Nm 405packet's path (in the network or in the hosts). 406.Sh TRYING DIFFERENT DATA PATTERNS 407The 408(inter)network 409layer should never treat packets differently depending on the data 410contained in the data portion. 411Unfortunately, data-dependent problems have been known to sneak into 412networks and remain undetected for long periods of time. 413In many cases the particular pattern that will have problems is something 414that does not have sufficient 415.Dq transitions , 416such as all ones or all zeros, or a pattern right at the edge, such as 417almost all zeros. 418It is not 419necessarily enough to specify a data pattern of all zeros (for example) 420on the command line because the pattern that is of interest is 421at the data link level, and the relationship between what you type and 422what the controllers transmit can be complicated. 423.Pp 424This means that if you have a data-dependent problem you will probably 425have to do a lot of testing to find it. 426If you are lucky, you may manage to find a file that either 427cannot 428be sent across your network or that takes much longer to transfer than 429other similar length files. 430You can then examine this file for repeated patterns that you can test 431using the 432.Fl p 433option of 434.Nm . 435.Sh TTL DETAILS 436The 437.Tn TTL 438value of an IP packet represents the maximum number of IP routers 439that the packet can go through before being thrown away. 440In current practice you can expect each router in the Internet to decrement 441the 442.Tn TTL 443field by exactly one. 444.Pp 445The 446.Tn TCP/IP 447specification recommends setting the 448.Tn TTL 449field for 450.Tn IP 451packets to 64, but many systems use smaller values 452.No ( Bx 4.3 453uses 30, 454.Bx 4.2 455used 15). 456.Pp 457The maximum possible value of this field is 255, and most 458.Ux 459systems set 460the 461.Tn TTL 462field of 463.Tn ICMP ECHO_REQUEST 464packets to 255. 465This is why you will find you can 466.Dq ping 467some hosts, but not reach them with 468.Xr telnet 1 469or 470.Xr ftp 1 . 471.Pp 472In normal operation 473.Nm 474prints the ttl value from the packet it receives. 475When a remote system receives a ping packet, it can do one of three things 476with the 477.Tn TTL 478field in its response: 479.Bl -bullet 480.It 481Not change it; this is what 482.Bx 483systems did before the 484.Bx 4.3 tahoe 485release. 486In this case the 487.Tn TTL 488value in the received packet will be 255 minus the 489number of routers in the round-trip path. 490.It 491Set it to 255; this is what current 492.Bx 493systems do. 494In this case the 495.Tn TTL 496value in the received packet will be 255 minus the 497number of routers in the path 498.Em from 499the remote system 500.Em to 501the 502.Nm Ns Em ing 503host. 504.It 505Set it to some other value. 506Some machines use the same value for 507.Tn ICMP 508packets that they use for 509.Tn TCP 510packets, for example either 30 or 60. 511Others may use completely wild values. 512.El 513.Sh EXIT STATUS 514The 515.Nm 516utility exits with one of the following values: 517.Bl -tag -width indent 518.It 0 519At least one response was heard from the specified 520.Ar host . 521.It 2 522The transmission was successful but no responses were received. 523.It any other value 524An error occurred. 525These values are defined in 526.In sysexits.h . 527.El 528.Sh SEE ALSO 529.Xr netstat 1 , 530.Xr icmp 4 , 531.Xr ifconfig 8 , 532.Xr routed 8 , 533.Xr traceroute 8 534.Sh HISTORY 535The 536.Nm 537utility appeared in 538.Bx 4.3 . 539.Sh AUTHORS 540The original 541.Nm 542utility was written by 543.An Mike Muuss 544while at the US Army Ballistics 545Research Laboratory. 546.Sh BUGS 547Many Hosts and Gateways ignore the 548.Tn RECORD_ROUTE 549option. 550.Pp 551The maximum IP header length is too small for options like 552.Tn RECORD_ROUTE 553to be completely useful. 554.No There Ap s 555not much that can be done about this, however. 556.Pp 557Flood pinging is not recommended in general, and flood pinging the 558broadcast address should only be done under very controlled conditions. 559.Pp 560The 561.Fl v 562option is not worth much on busy hosts. 563