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 November 26, 2020 32.Dt PING 8 33.Os 34.Sh NAME 35.Nm ping 36.Nd send 37.Tn ICMP 38or 39.Tn ICMPv6 ECHO_REQUEST 40packets to network hosts 41.Sh SYNOPSIS 42.Nm 43.Op Fl 4AaDdfHnoQqRrv 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 C Ar pcp 64.Op Fl c Ar count 65.Op Fl I Ar iface 66.Op Fl i Ar wait 67.Op Fl l Ar preload 68.Op Fl M Cm mask | time 69.Op Fl m Ar ttl 70.Op Fl P Ar policy 71.Op Fl p Ar pattern 72.Op Fl S Ar src_addr 73.Op Fl s Ar packetsize 74.Op Fl T Ar ttl 75.Op Fl t Ar timeout 76.Op Fl W Ar waittime 77.Op Fl z Ar tos 78.Ar IPv4-mcast-group 79.Nm 80.Op Fl 6AaDdEfHNnOoquvYyZ 81.Op Fl b Ar bufsiz 82.Op Fl c Ar count 83.Op Fl e Ar gateway 84.Op Fl I Ar interface 85.Op Fl i Ar wait 86.Op Fl k Ar addrtype 87.Op Fl l Ar preload 88.Op Fl m Ar hoplimit 89.Op Fl P Ar policy 90.Op Fl p Ar pattern 91.Op Fl S Ar sourceaddr 92.Op Fl s Ar packetsize 93.Op Fl t Ar timeout 94.Op Fl W Ar waittime 95.Op Ar IPv6-hops ... 96.Ar IPv6-host 97.Sh DESCRIPTION 98The 99.Nm 100utility invoked with an IPv4 target 101.Ns ( Ar IPv4-host No or Ar IPv4-mcast-group Ns ) 102uses the 103.Tn ICMP 104.No protocol Ap s mandatory 105.Tn ECHO_REQUEST 106datagram to elicit an 107.Tn ICMP ECHO_RESPONSE 108from a host or gateway. 109.Tn ECHO_REQUEST 110datagrams 111.Pq Dq pings 112have an IP and 113.Tn ICMP 114header, followed by a 115.Dq struct timeval 116and then an arbitrary number of 117.Dq pad 118bytes used to fill out the packet. 119.Pp 120When invoked with an IPv6 target 121.Ns ( Ar IPv6-host Ns ) Ns , 122it uses the 123.Tn ICMPv6 124protocol's mandatory 125.Tn ICMP6_ECHO_REQUEST 126datagram to elicit an 127.Tn ICMP6_ECHO_REPLY 128.Ns . 129.Tn ICMP6_ECHO_REQUEST 130datagrams have an IPv6 header and 131.Tn ICMPv6 132header formatted as documented in RFC 2463. 133.Pp 134When invoked with a hostname, the version to which the target is resolved first is used. 135In that case, the options and arguments used must be valid for the specific IP version, otherwise 136.Nm 137exits with an error. 138If the target is resolved to both IPv4 and IPv6, the specific IP version can be requested by 139.Fl 4 140or 141.Fl 6 142options, respectively. 143For backwards-compatibility, ICMPv6 can also be selected by invoking the binary 144as 145.Nm ping6 . 146.Ss Options common to both IPv4 and IPv6 targets 147.Bl -tag -width indent 148.It Fl A 149Audible. 150Output a bell 151.Tn ( ASCII 1520x07) 153character when no packet is received before the next packet 154is transmitted. 155To cater for round-trip times that are longer than the interval 156between transmissions, further missing packets cause a bell only 157if the maximum number of unreceived packets has increased. 158.It Fl a 159Audible. 160Include a bell 161.Tn ( ASCII 1620x07) 163character in the output when any packet is received. 164.It Fl C Ar pcp 165Add an 802.1p Ethernet Priority Code Point when sending a packet. 1660..7 uses that specific PCP, -1 uses the interface default PCP (or none). 167.It Fl c Ar count 168Stop after sending 169(and receiving) 170.Ar count 171.Tn ECHO_RESPONSE 172packets. 173If this option is not specified, 174.Nm 175will operate until interrupted. 176.Pp 177For an IPv4 target, if this option is specified in conjunction with ping sweeps, 178each sweep will consist of 179.Ar count 180packets. 181.It Fl D 182Disable fragmentation. 183.It Fl d 184Set the 185.Dv SO_DEBUG 186option on the socket being used. 187.It Fl f 188Flood ping. 189Outputs packets as fast as they come back or one hundred times per second, 190whichever is more. 191For every 192.Tn ECHO_REQUEST 193sent a period 194.Dq .\& 195is printed, while for every 196.Tn ECHO_REPLY 197received a backspace is printed. 198This provides a rapid display of how many packets are being dropped. 199Only the super-user may use this option. 200.Bf -emphasis 201This can be very hard on a network and should be used with caution. 202.Ef 203.It Fl H 204Hostname output. 205Try to do a reverse DNS lookup when displaying addresses. 206This is the opposite of the 207.Fl n 208option. 209.It Fl I Ar iface 210For an IPv4 target, 211.Ar iface 212is an IP address indentifying an interface from which the packets will be sent. 213This flag applies only if the ping target is a multicast address. 214.Pp 215For an IPv6 target, 216.Ar iface 217is a name of an interface (e.g. `em0') from which the packets will be sent. 218This flag applies if the ping target is a multicast address, or link-local/site-local 219unicast address. 220.It Fl i Ar wait 221Wait 222.Ar wait 223seconds 224.Em between sending each packet . 225The default is to wait for one second between each packet. 226The wait time may be fractional, but only the super-user may specify 227values less than 1 second. 228This option is incompatible with the 229.Fl f 230option. 231.It Fl l Ar preload 232If 233.Ar preload 234is specified, 235.Nm 236sends that many packets as fast as possible before falling into its normal 237mode of behavior. 238Only the super-user may use this option. 239.It Fl m Ar ttl 240For an IPv4 target, set the IP Time To Live for outgoing packets. 241If not specified, the kernel uses the value of the 242.Va net.inet.ip.ttl 243MIB variable. 244.Pp 245For an IPv6 target, set the IPv6 hoplimit. 246.It Fl n 247Numeric output only. 248No attempt will be made to lookup symbolic names for host addresses. 249This is the opposite of 250.Fl H , 251and it is the default behavior. 252.It Fl o 253Exit successfully after receiving one reply packet. 254.It Fl P Ar policy 255.Ar policy 256specifies IPsec policy for the ping session. 257For details please refer to 258.Xr ipsec 4 259and 260.Xr ipsec_set_policy 3 . 261.It Fl p Ar pattern 262You may specify up to 16 263.Dq pad 264bytes to fill out the packet you send. 265This is useful for diagnosing data-dependent problems in a network. 266For example, 267.Dq Li \-p ff 268will cause the sent packet to be filled with all 269ones. 270.It Fl q 271Quiet output. 272Nothing is displayed except the summary lines at startup time and 273when finished. 274.It Fl S Ar src_addr 275Use the following IP address as the source address in outgoing packets. 276On hosts with more than one IP address, this option can be used to 277force the source address to be something other than the IP address 278of the interface the probe packet is sent on. 279.Pp 280For IPv4, if the IP address is not one of this machine's interface 281addresses, an error is returned and nothing is sent. 282.Pp 283For IPv6, the source address must be one of the unicast addresses of 284the sending node, and must be numeric. 285.It Fl s Ar packetsize 286Specify the number of data bytes to be sent. 287The default is 56, which translates into 64 288.Tn ICMP 289data bytes when combined 290with the 8 bytes of 291.Tn ICMP 292header data. 293.Pp 294For IPv4, only the super-user may specify values more than default. 295This option cannot be used with ping sweeps. 296.Pp 297For IPv6, you may need to specify 298.Fl b 299as well to extend socket buffer size. 300.It Fl t Ar timeout 301Specify a timeout, in seconds, before ping exits regardless of how 302many packets have been received. 303.It Fl v 304Verbose output. 305.Tn ICMP 306packets other than 307.Tn ECHO_RESPONSE 308that are received are listed. 309.It Fl W Ar waittime 310Time in milliseconds to wait for a reply for each packet sent. 311If a reply arrives later, the packet is not printed as replied, but 312considered as replied when calculating statistics. 313.El 314.Ss Options only for IPv4 targets 315.Bl -tag -width indent 316.It Fl 4 317Use IPv4 regardless of how the target is resolved. 318.It Fl G Ar sweepmaxsize 319Specify the maximum size of 320.Tn ICMP 321payload when sending sweeping pings. 322This option is required for ping sweeps. 323.It Fl g Ar sweepminsize 324Specify the size of 325.Tn ICMP 326payload to start with when sending sweeping pings. 327The default value is 0. 328.It Fl h Ar sweepincrsize 329Specify the number of bytes to increment the size of 330.Tn ICMP 331payload after 332each sweep when sending sweeping pings. 333The default value is 1. 334.It Fl L 335Suppress loopback of multicast packets. 336This flag only applies if the ping destination is a multicast address. 337.It Fl M Cm mask | time 338Use 339.Dv ICMP_MASKREQ 340or 341.Dv ICMP_TSTAMP 342instead of 343.Dv ICMP_ECHO . 344For 345.Cm mask , 346print the netmask of the remote machine. 347Set the 348.Va net.inet.icmp.maskrepl 349MIB variable to enable 350.Dv ICMP_MASKREPLY 351and 352.Va net.inet.icmp.maskfake 353if you want to override the netmask in the response. 354For 355.Cm time , 356print the origination, reception and transmission timestamps. 357Set the 358.Va net.inet.icmp.tstamprepl 359MIB variable to enable or disable 360.Dv ICMP_TSTAMPREPLY . 361.It Fl Q 362Somewhat quiet output. 363.No Don Ap t 364display ICMP error messages that are in response to our query messages. 365Originally, the 366.Fl v 367flag was required to display such errors, but 368.Fl v 369displays all ICMP error messages. 370On a busy machine, this output can be overbearing. 371Without the 372.Fl Q 373flag, 374.Nm 375prints out any ICMP error messages caused by its own ECHO_REQUEST 376messages. 377.It Fl R 378Record route. 379Includes the 380.Tn RECORD_ROUTE 381option in the 382.Tn ECHO_REQUEST 383packet and displays 384the route buffer on returned packets. 385Note that the IP header is only large enough for nine such routes; 386the 387.Xr traceroute 8 388command is usually better at determining the route packets take to a 389particular destination. 390If more routes come back than should, such as due to an illegal spoofed 391packet, ping will print the route list and then truncate it at the correct 392spot. 393Many hosts ignore or discard the 394.Tn RECORD_ROUTE 395option. 396.It Fl r 397Bypass the normal routing tables and send directly to a host on an attached 398network. 399If the host is not on a directly-attached network, an error is returned. 400This option can be used to ping a local host through an interface 401that has no route through it 402(e.g., after the interface was dropped by 403.Xr routed 8 ) . 404.It Fl T Ar ttl 405Set the IP Time To Live for multicasted packets. 406This flag only applies if the ping destination is a multicast address. 407.It Fl z Ar tos 408Use the specified type of service. 409.It Ar IPv4-host 410hostname or IPv4 address of the final destination node. 411.It Ar IPv4-mcast-group 412IPv4 multicast address of the final destination nodes. 413.El 414.Ss Options only for IPv6 targets 415.Bl -tag -width indent 416.It Fl 6 417Use IPv6 regardless of how the target is resolved. 418.It Fl b Ar bufsiz 419Set socket buffer size. 420.It Fl e Ar gateway 421Specifies to use 422.Ar gateway 423as the next hop to the destination. 424The gateway must be a neighbor of the sending node. 425.It Fl k Ar addrtype 426Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. 427.Ar addrtype 428must be a string constructed of the following characters. 429.Bl -tag -width Ds -compact 430.It Ic a 431requests unicast addresses from all of the responder's interfaces. 432If the character is omitted, 433only those addresses which belong to the interface which has the 434responder's address are requests. 435.It Ic c 436requests responder's IPv4-compatible and IPv4-mapped addresses. 437.It Ic g 438requests responder's global-scope addresses. 439.It Ic s 440requests responder's site-local addresses. 441.It Ic l 442requests responder's link-local addresses. 443.It Ic A 444requests responder's anycast addresses. 445Without this character, the responder will return unicast addresses only. 446With this character, the responder will return anycast addresses only. 447Note that the specification does not specify how to get responder's 448anycast addresses. 449This is an experimental option. 450.El 451.It Fl N 452Probe node information multicast group address 453.Pq Li ff02::2:ffxx:xxxx . 454.Ar host 455must be string hostname of the target 456(must not be a numeric IPv6 address). 457Node information multicast group will be computed based on given 458.Ar host , 459and will be used as the final destination. 460Since node information multicast group is a link-local multicast group, 461outgoing interface needs to be specified by 462.Fl I 463option. 464.Pp 465When specified twice, the address 466.Pq Li ff02::2:xxxx:xxxx 467is used instead. 468The former is in RFC 4620, the latter is in an old Internet Draft 469draft-ietf-ipngwg-icmp-name-lookup. 470Note that KAME-derived implementations including 471.Fx 472use the latter. 473.It Fl O 474Generate ICMPv6 Node Information supported query types query, 475rather than echo-request. 476.Fl s 477has no effect if 478.Fl O 479is specified. 480.It Fl u 481By default, 482.Nm 483asks the kernel to fragment packets to fit into the minimum IPv6 MTU. 484The 485.Fl u 486option 487will suppress the behavior in the following two levels: 488when the option is specified once, the behavior will be disabled for 489unicast packets. 490When the option is more than once, it will be disabled for both 491unicast and multicast packets. 492.It Fl Y 493Same as 494.Fl y , 495but with old packet format based on 03 draft. 496This option is present for backward compatibility. 497.Fl s 498has no effect if 499.Fl y 500is specified. 501.It Fl y 502Generate ICMPv6 Node Information DNS Name query, rather than echo-request. 503.Fl s 504has no effect if 505.Fl y 506is specified. 507.It Ar IPv6-hops 508IPv6 addresses for intermediate nodes, 509which will be put into type 0 routing header. 510.It Ar IPv6-host 511IPv6 address of the final destination node. 512.El 513.Ss Experimental options only for IPv6 target 514.Bl -tag -width indent 515.It Fl E 516Enables transport-mode IPsec encapsulated security payload. 517.It Fl Z 518Enables transport-mode IPsec authentication header. 519.El 520.Pp 521When using 522.Nm 523for fault isolation, it should first be run on the local host, to verify 524that the local network interface is up and running. 525Then, hosts and gateways further and further away should be 526.Dq pinged . 527Round-trip times and packet loss statistics are computed. 528If duplicate packets are received, they are not included in the packet 529loss calculation, although the round trip time of these packets is used 530in calculating the round-trip time statistics. 531When the specified number of packets have been sent 532(and received) 533or if the program is terminated with a 534.Dv SIGINT , 535a brief summary is displayed, showing the number of packets sent and 536received, and the minimum, mean, maximum, and standard deviation of 537the round-trip times. 538.Pp 539If 540.Nm 541receives a 542.Dv SIGINFO 543(see the 544.Cm status 545argument for 546.Xr stty 1 ) 547signal, the current number of packets sent and received, and the 548minimum, mean, maximum, and standard deviation of the round-trip times 549will be written to the standard output. 550.Pp 551This program is intended for use in network testing, measurement and 552management. 553Because of the load it can impose on the network, it is unwise to use 554.Nm 555during normal operations or from automated scripts. 556.Sh ICMP PACKET DETAILS 557An IP header without options is 20 bytes. 558An 559.Tn ICMP 560.Tn ECHO_REQUEST 561packet contains an additional 8 bytes worth of 562.Tn ICMP 563header followed by an arbitrary amount of data. 564When a 565.Ar packetsize 566is given, this indicated the size of this extra piece of data 567(the default is 56). 568Thus the amount of data received inside of an IP packet of type 569.Tn ICMP 570.Tn ECHO_REPLY 571will always be 8 bytes more than the requested data space 572(the 573.Tn ICMP 574header). 575.Pp 576If the data space is at least eight bytes large, 577.Nm 578uses the first eight bytes of this space to include a timestamp which 579it uses in the computation of round trip times. 580If less than eight bytes of pad are specified, no round trip times are 581given. 582.Sh DUPLICATE AND DAMAGED PACKETS 583The 584.Nm 585utility will report duplicate and damaged packets. 586Duplicate packets should never occur when pinging a unicast address, 587and seem to be caused by 588inappropriate link-level retransmissions. 589Duplicates may occur in many situations and are rarely 590(if ever) 591a good sign, although the presence of low levels of duplicates may not 592always be cause for alarm. 593Duplicates are expected when pinging a broadcast or multicast address, 594since they are not really duplicates but replies from different hosts 595to the same request. 596.Pp 597Damaged packets are obviously serious cause for alarm and often 598indicate broken hardware somewhere in the 599.Nm 600packet's path (in the network or in the hosts). 601.Sh TRYING DIFFERENT DATA PATTERNS 602The 603(inter)network 604layer should never treat packets differently depending on the data 605contained in the data portion. 606Unfortunately, data-dependent problems have been known to sneak into 607networks and remain undetected for long periods of time. 608In many cases the particular pattern that will have problems is something 609that does not have sufficient 610.Dq transitions , 611such as all ones or all zeros, or a pattern right at the edge, such as 612almost all zeros. 613It is not 614necessarily enough to specify a data pattern of all zeros (for example) 615on the command line because the pattern that is of interest is 616at the data link level, and the relationship between what you type and 617what the controllers transmit can be complicated. 618.Pp 619This means that if you have a data-dependent problem you will probably 620have to do a lot of testing to find it. 621If you are lucky, you may manage to find a file that either 622cannot 623be sent across your network or that takes much longer to transfer than 624other similar length files. 625You can then examine this file for repeated patterns that you can test 626using the 627.Fl p 628option of 629.Nm . 630.Sh IPv4 TTL DETAILS 631The 632.Tn TTL 633value of an IP packet represents the maximum number of IP routers 634that the packet can go through before being thrown away. 635In current practice you can expect each router in the Internet to decrement 636the 637.Tn TTL 638field by exactly one. 639.Pp 640The 641.Tn TCP/IP 642specification recommends setting the 643.Tn TTL 644field for 645.Tn IP 646packets to 64, but many systems use smaller values 647.No ( Bx 4.3 648uses 30, 649.Bx 4.2 650used 15). 651.Pp 652The maximum possible value of this field is 255, and most 653.Ux 654systems set 655the 656.Tn TTL 657field of 658.Tn ICMP ECHO_REQUEST 659packets to 255. 660This is why you will find you can 661.Dq ping 662some hosts, but not reach them with 663.Xr telnet 1 664or 665.Xr ftp 1 . 666.Pp 667In normal operation 668.Nm 669prints the ttl value from the packet it receives. 670When a remote system receives a ping packet, it can do one of three things 671with the 672.Tn TTL 673field in its response: 674.Bl -bullet 675.It 676Not change it; this is what 677.Bx 678systems did before the 679.Bx 4.3 tahoe 680release. 681In this case the 682.Tn TTL 683value in the received packet will be 255 minus the 684number of routers in the round-trip path. 685.It 686Set it to 255; this is what current 687.Bx 688systems do. 689In this case the 690.Tn TTL 691value in the received packet will be 255 minus the 692number of routers in the path 693.Em from 694the remote system 695.Em to 696the 697.Nm Ns Em ing 698host. 699.It 700Set it to some other value. 701Some machines use the same value for 702.Tn ICMP 703packets that they use for 704.Tn TCP 705packets, for example either 30 or 60. 706Others may use completely wild values. 707.El 708.Sh EXIT STATUS 709The 710.Nm 711utility exits with one of the following values: 712.Bl -tag -width indent 713.It 0 714At least one response was heard from the specified 715.Ar host . 716.It 2 717The transmission was successful but no responses were received. 718.It any other value 719An error occurred. 720.El 721.Sh EXAMPLES 722The following will send ICMPv6 echo request to 723.Li dst.foo.com . 724.Bd -literal -offset indent 725ping -6 -n dst.foo.com 726.Ed 727.Pp 728The following will probe hostnames for all nodes on the network link attached to 729.Li wi0 730interface. 731The address 732.Li ff02::1 733is named the link-local all-node multicast address, and the packet would 734reach every node on the network link. 735.Bd -literal -offset indent 736ping -6 -y ff02::1%wi0 737.Ed 738.Pp 739The following will probe addresses assigned to the destination node, 740.Li dst.foo.com . 741.Bd -literal -offset indent 742ping -6 -k agl dst.foo.com 743.Ed 744.Sh SEE ALSO 745.Xr netstat 1 , 746.Xr icmp 4 , 747.Xr icmp6 4 , 748.Xr inet6 4 , 749.Xr ip6 4 , 750.Xr ifconfig 8 , 751.Xr routed 8 , 752.Xr traceroute 8 , 753.Xr traceroute6 8 754.Rs 755.%A A. Conta 756.%A S. Deering 757.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification" 758.%N RFC 2463 759.%D December 1998 760.Re 761.Rs 762.%A Matt Crawford 763.%T "IPv6 Node Information Queries" 764.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt 765.%D May 2002 766.%O work in progress material 767.Re 768.Sh HISTORY 769The 770.Nm 771utility appeared in 772.Bx 4.3 . 773The 774.Nm ping6 775utility with IPv6 support first appeared in the WIDE Hydrangea IPv6 776protocol stack kit. 777.Pp 778IPv6 and IPsec support based on the KAME Project 779.Pq Pa http://www.kame.net/ 780stack was initially integrated into 781.Fx 4.0 . 782.Pp 783The 784.Nm ping6 785utility was merged to 786.Nm 787in Google Summer of Code 2019. 788.Sh AUTHORS 789The original 790.Nm 791utility was written by 792.An Mike Muuss 793while at the US Army Ballistics 794Research Laboratory. 795.Sh BUGS 796Many Hosts and Gateways ignore the IPv4 797.Tn RECORD_ROUTE 798option. 799.Pp 800The maximum IP header length is too small for options like 801.Tn RECORD_ROUTE 802to be completely useful. 803.No There Ap s 804not much that can be done about this, however. 805.Pp 806Flood pinging is not recommended in general, and flood pinging the 807broadcast address should only be done under very controlled conditions. 808.Pp 809The 810.Fl v 811option is not worth much on busy hosts. 812