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.\" 4. 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 April 4, 2006 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 . 205For 206.Cm time , 207print the origination, reception and transmission timestamps. 208.It Fl m Ar ttl 209Set the IP Time To Live for outgoing packets. 210If not specified, the kernel uses the value of the 211.Va net.inet.ip.ttl 212MIB variable. 213.It Fl n 214Numeric output only. 215No attempt will be made to lookup symbolic names for host addresses. 216.It Fl o 217Exit successfully after receiving one reply packet. 218.It Fl P Ar policy 219.Ar policy 220specifies IPsec policy for the ping session. 221For details please refer to 222.Xr ipsec 4 223and 224.Xr ipsec_set_policy 3 . 225.It Fl p Ar pattern 226You may specify up to 16 227.Dq pad 228bytes to fill out the packet you send. 229This is useful for diagnosing data-dependent problems in a network. 230For example, 231.Dq Li \-p ff 232will cause the sent packet to be filled with all 233ones. 234.It Fl Q 235Somewhat quiet output. 236.No Don Ap t 237display ICMP error messages that are in response to our query messages. 238Originally, the 239.Fl v 240flag was required to display such errors, but 241.Fl v 242displays all ICMP error messages. 243On a busy machine, this output can be overbearing. 244Without the 245.Fl Q 246flag, 247.Nm 248prints out any ICMP error messages caused by its own ECHO_REQUEST 249messages. 250.It Fl q 251Quiet output. 252Nothing is displayed except the summary lines at startup time and 253when finished. 254.It Fl R 255Record route. 256Includes the 257.Tn RECORD_ROUTE 258option in the 259.Tn ECHO_REQUEST 260packet and displays 261the route buffer on returned packets. 262Note that the IP header is only large enough for nine such routes; 263the 264.Xr traceroute 8 265command is usually better at determining the route packets take to a 266particular destination. 267If more routes come back than should, such as due to an illegal spoofed 268packet, ping will print the route list and then truncate it at the correct 269spot. 270Many hosts ignore or discard the 271.Tn RECORD_ROUTE 272option. 273.It Fl r 274Bypass the normal routing tables and send directly to a host on an attached 275network. 276If the host is not on a directly-attached network, an error is returned. 277This option can be used to ping a local host through an interface 278that has no route through it 279(e.g., after the interface was dropped by 280.Xr routed 8 ) . 281.It Fl S Ar src_addr 282Use the following IP address as the source address in outgoing packets. 283On hosts with more than one IP address, this option can be used to 284force the source address to be something other than the IP address 285of the interface the probe packet is sent on. 286If the IP address 287is not one of this machine's interface addresses, an error is 288returned and nothing is sent. 289.It Fl s Ar packetsize 290Specify the number of data bytes to be sent. 291The default is 56, which translates into 64 292.Tn ICMP 293data bytes when combined 294with the 8 bytes of 295.Tn ICMP 296header data. 297Only the super-user may specify values more than default. 298This option cannot be used with ping sweeps. 299.It Fl T Ar ttl 300Set the IP Time To Live for multicasted packets. 301This flag only applies if the ping destination is a multicast address. 302.It Fl t Ar timeout 303Specify a timeout, in seconds, before ping exits regardless of how 304many packets have been received. 305.It Fl v 306Verbose output. 307.Tn ICMP 308packets other than 309.Tn ECHO_RESPONSE 310that are received are listed. 311.It Fl W Ar waittime 312Time in milliseconds to wait for a reply for each packet sent. 313If a reply arrives later, the packet is not printed as replied, but 314considered as replied when calculating statistics. 315.It Fl z Ar tos 316Use the specified type of service. 317.El 318.Pp 319When using 320.Nm 321for fault isolation, it should first be run on the local host, to verify 322that the local network interface is up and running. 323Then, hosts and gateways further and further away should be 324.Dq pinged . 325Round-trip times and packet loss statistics are computed. 326If duplicate packets are received, they are not included in the packet 327loss calculation, although the round trip time of these packets is used 328in calculating the round-trip time statistics. 329When the specified number of packets have been sent 330(and received) 331or if the program is terminated with a 332.Dv SIGINT , 333a brief summary is displayed, showing the number of packets sent and 334received, and the minimum, mean, maximum, and standard deviation of 335the round-trip times. 336.Pp 337If 338.Nm 339receives a 340.Dv SIGINFO 341(see the 342.Cm status 343argument for 344.Xr stty 1 ) 345signal, the current number of packets sent and received, and the 346minimum, mean, and maximum of the round-trip times will be written to 347the standard error output. 348.Pp 349This program is intended for use in network testing, measurement and 350management. 351Because of the load it can impose on the network, it is unwise to use 352.Nm 353during normal operations or from automated scripts. 354.Sh ICMP PACKET DETAILS 355An IP header without options is 20 bytes. 356An 357.Tn ICMP 358.Tn ECHO_REQUEST 359packet contains an additional 8 bytes worth of 360.Tn ICMP 361header followed by an arbitrary amount of data. 362When a 363.Ar packetsize 364is given, this indicated the size of this extra piece of data 365(the default is 56). 366Thus the amount of data received inside of an IP packet of type 367.Tn ICMP 368.Tn ECHO_REPLY 369will always be 8 bytes more than the requested data space 370(the 371.Tn ICMP 372header). 373.Pp 374If the data space is at least eight bytes large, 375.Nm 376uses the first eight bytes of this space to include a timestamp which 377it uses in the computation of round trip times. 378If less than eight bytes of pad are specified, no round trip times are 379given. 380.Sh DUPLICATE AND DAMAGED PACKETS 381The 382.Nm 383utility will report duplicate and damaged packets. 384Duplicate packets should never occur when pinging a unicast address, 385and seem to be caused by 386inappropriate link-level retransmissions. 387Duplicates may occur in many situations and are rarely 388(if ever) 389a good sign, although the presence of low levels of duplicates may not 390always be cause for alarm. 391Duplicates are expected when pinging a broadcast or multicast address, 392since they are not really duplicates but replies from different hosts 393to the same request. 394.Pp 395Damaged packets are obviously serious cause for alarm and often 396indicate broken hardware somewhere in the 397.Nm 398packet's path (in the network or in the hosts). 399.Sh TRYING DIFFERENT DATA PATTERNS 400The 401(inter)network 402layer should never treat packets differently depending on the data 403contained in the data portion. 404Unfortunately, data-dependent problems have been known to sneak into 405networks and remain undetected for long periods of time. 406In many cases the particular pattern that will have problems is something 407that does not have sufficient 408.Dq transitions , 409such as all ones or all zeros, or a pattern right at the edge, such as 410almost all zeros. 411It is not 412necessarily enough to specify a data pattern of all zeros (for example) 413on the command line because the pattern that is of interest is 414at the data link level, and the relationship between what you type and 415what the controllers transmit can be complicated. 416.Pp 417This means that if you have a data-dependent problem you will probably 418have to do a lot of testing to find it. 419If you are lucky, you may manage to find a file that either 420cannot 421be sent across your network or that takes much longer to transfer than 422other similar length files. 423You can then examine this file for repeated patterns that you can test 424using the 425.Fl p 426option of 427.Nm . 428.Sh TTL DETAILS 429The 430.Tn TTL 431value of an IP packet represents the maximum number of IP routers 432that the packet can go through before being thrown away. 433In current practice you can expect each router in the Internet to decrement 434the 435.Tn TTL 436field by exactly one. 437.Pp 438The 439.Tn TCP/IP 440specification recommends setting the 441.Tn TTL 442field for 443.Tn IP 444packets to 64, but many systems use smaller values 445.No ( Bx 4.3 446uses 30, 447.Bx 4.2 448used 15). 449.Pp 450The maximum possible value of this field is 255, and most 451.Ux 452systems set 453the 454.Tn TTL 455field of 456.Tn ICMP ECHO_REQUEST 457packets to 255. 458This is why you will find you can 459.Dq ping 460some hosts, but not reach them with 461.Xr telnet 1 462or 463.Xr ftp 1 . 464.Pp 465In normal operation 466.Nm 467prints the ttl value from the packet it receives. 468When a remote system receives a ping packet, it can do one of three things 469with the 470.Tn TTL 471field in its response: 472.Bl -bullet 473.It 474Not change it; this is what 475.Bx 476systems did before the 477.Bx 4.3 tahoe 478release. 479In this case the 480.Tn TTL 481value in the received packet will be 255 minus the 482number of routers in the round-trip path. 483.It 484Set it to 255; this is what current 485.Bx 486systems do. 487In this case the 488.Tn TTL 489value in the received packet will be 255 minus the 490number of routers in the path 491.Em from 492the remote system 493.Em to 494the 495.Nm Ns Em ing 496host. 497.It 498Set it to some other value. 499Some machines use the same value for 500.Tn ICMP 501packets that they use for 502.Tn TCP 503packets, for example either 30 or 60. 504Others may use completely wild values. 505.El 506.Sh RETURN VALUES 507The 508.Nm 509utility returns an exit status of zero if at least one response was 510heard from the specified 511.Ar host ; 512a status of two if the transmission was successful but no responses 513were received; or another value 514(from 515.In sysexits.h ) 516if an error occurred. 517.Sh SEE ALSO 518.Xr netstat 1 , 519.Xr ifconfig 8 , 520.Xr routed 8 , 521.Xr traceroute 8 522.Sh HISTORY 523The 524.Nm 525utility appeared in 526.Bx 4.3 . 527.Sh AUTHORS 528The original 529.Nm 530utility was written by 531.An Mike Muuss 532while at the US Army Ballistics 533Research Laboratory. 534.Sh BUGS 535Many Hosts and Gateways ignore the 536.Tn RECORD_ROUTE 537option. 538.Pp 539The maximum IP header length is too small for options like 540.Tn RECORD_ROUTE 541to be completely useful. 542.No There Ap s 543not much that can be done about this, however. 544.Pp 545Flood pinging is not recommended in general, and flood pinging the 546broadcast address should only be done under very controlled conditions. 547.Pp 548The 549.Fl v 550option is not worth much on busy hosts. 551