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 24, 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 135resolved first is used. In that case, the options and arguments used 136must be valid for the specific IP version, otherwise 137.Nm 138exits with an error. If the target is resolved to both IPv4 and IPv6, 139the specific IP version can be requested by 140.Fl 4 141or 142.Fl 6 143options, respectively. 144.Ss Options common to both IPv4 and IPv6 targets 145.Bl -tag -width indent 146.It Fl A 147Audible. 148Output a bell 149.Tn ( ASCII 1500x07) 151character when no packet is received before the next packet 152is transmitted. 153To cater for round-trip times that are longer than the interval 154between transmissions, further missing packets cause a bell only 155if the maximum number of unreceived packets has increased. 156.It Fl a 157Audible. 158Include a bell 159.Tn ( ASCII 1600x07) 161character in the output when any packet is received. 162.It Fl C Ar pcp 163Add an 802.1p Ethernet Priority Code Point when sending a packet. 1640..7 uses that specific PCP, -1 uses the interface default PCP (or none). 165.It Fl c Ar count 166Stop after sending 167(and receiving) 168.Ar count 169.Tn ECHO_RESPONSE 170packets. 171If this option is not specified, 172.Nm 173will operate until interrupted. 174.Pp 175For an IPv4 target, if this option is specified in conjunction with ping sweeps, 176each sweep will consist of 177.Ar count 178packets. 179.It Fl D 180Disable fragmentation. 181.It Fl d 182Set the 183.Dv SO_DEBUG 184option on the socket being used. 185.It Fl f 186Flood ping. 187Outputs packets as fast as they come back or one hundred times per second, 188whichever is more. 189For every 190.Tn ECHO_REQUEST 191sent a period 192.Dq .\& 193is printed, while for every 194.Tn ECHO_REPLY 195received a backspace is printed. 196This provides a rapid display of how many packets are being dropped. 197Only the super-user may use this option. 198.Bf -emphasis 199This can be very hard on a network and should be used with caution. 200.Ef 201.It Fl H 202Hostname output. 203Try to do a reverse DNS lookup when displaying addresses. 204This is the opposite of the 205.Fl n 206option. 207.It Fl I Ar iface 208For an IPv4 target, 209.Ar iface 210is an IP address indentifying an interface from which the packets will 211be sent. This flag applies only if the ping target is a multicast 212address. 213.Pp 214For an IPv6 target, 215.Ar iface 216is a name of an interface (e.g. `em0') from which the packets will be 217sent. This flag applies if the ping target is a multicast address, or 218link-local/site-local unicast address. 219.It Fl i Ar wait 220Wait 221.Ar wait 222seconds 223.Em between sending each packet . 224The default is to wait for one second between each packet. 225The wait time may be fractional, but only the super-user may specify 226values less than 1 second. 227This option is incompatible with the 228.Fl f 229option. 230.It Fl l Ar preload 231If 232.Ar preload 233is specified, 234.Nm 235sends that many packets as fast as possible before falling into its normal 236mode of behavior. 237Only the super-user may use this option. 238.It Fl m Ar ttl 239For an IPv4 target, set the IP Time To Live for outgoing packets. 240If not specified, the kernel uses the value of the 241.Va net.inet.ip.ttl 242MIB variable. 243.Pp 244For an IPv6 target, set the IPv6 hoplimit. 245.It Fl n 246Numeric output only. 247No attempt will be made to lookup symbolic names for host addresses. 248This is the opposite of 249.Fl H , 250and it is the default behavior. 251.It Fl o 252Exit successfully after receiving one reply packet. 253.It Fl P Ar policy 254.Ar policy 255specifies IPsec policy for the ping session. 256For details please refer to 257.Xr ipsec 4 258and 259.Xr ipsec_set_policy 3 . 260.It Fl p Ar pattern 261You may specify up to 16 262.Dq pad 263bytes to fill out the packet you send. 264This is useful for diagnosing data-dependent problems in a network. 265For example, 266.Dq Li \-p ff 267will cause the sent packet to be filled with all 268ones. 269.It Fl q 270Quiet output. 271Nothing is displayed except the summary lines at startup time and 272when finished. 273.It Fl S Ar src_addr 274Use the following IP address as the source address in outgoing packets. 275On hosts with more than one IP address, this option can be used to 276force the source address to be something other than the IP address 277of the interface the probe packet is sent on. 278.Pp 279For IPv4, if the IP address is not one of this machine's interface 280addresses, an error is returned and nothing is sent. 281.Pp 282For IPv6, the source address must be one of the unicast addresses of 283the sending node, and must be numeric. 284.It Fl s Ar packetsize 285Specify the number of data bytes to be sent. 286The default is 56, which translates into 64 287.Tn ICMP 288data bytes when combined 289with the 8 bytes of 290.Tn ICMP 291header data. 292.Pp 293For IPv4, only the super-user may specify values more than default. 294This option cannot be used with ping sweeps. 295.Pp 296For IPv6, you may need to specify 297.Fl b 298as well to extend socket buffer size. 299.It Fl t Ar timeout 300Specify a timeout, in seconds, before ping exits regardless of how 301many packets have been received. 302.It Fl v 303Verbose output. 304.Tn ICMP 305packets other than 306.Tn ECHO_RESPONSE 307that are received are listed. 308.It Fl W Ar waittime 309Time in milliseconds to wait for a reply for each packet sent. 310If a reply arrives later, the packet is not printed as replied, but 311considered as replied when calculating statistics. 312.El 313.Ss Options only for IPv4 targets 314.Bl -tag -width indent 315.It Fl 4 316Use IPv4 regardless of how the target is resolved. 317.It Fl G Ar sweepmaxsize 318Specify the maximum size of 319.Tn ICMP 320payload when sending sweeping pings. 321This option is required for ping sweeps. 322.It Fl g Ar sweepminsize 323Specify the size of 324.Tn ICMP 325payload to start with when sending sweeping pings. 326The default value is 0. 327.It Fl h Ar sweepincrsize 328Specify the number of bytes to increment the size of 329.Tn ICMP 330payload after 331each sweep when sending sweeping pings. 332The default value is 1. 333.It Fl L 334Suppress loopback of multicast packets. 335This flag only applies if the ping destination is a multicast address. 336.It Fl M Cm mask | time 337Use 338.Dv ICMP_MASKREQ 339or 340.Dv ICMP_TSTAMP 341instead of 342.Dv ICMP_ECHO . 343For 344.Cm mask , 345print the netmask of the remote machine. 346Set the 347.Va net.inet.icmp.maskrepl 348MIB variable to enable 349.Dv ICMP_MASKREPLY 350and 351.Va net.inet.icmp.maskfake 352if you want to override the netmask in the response. 353For 354.Cm time , 355print the origination, reception and transmission timestamps. 356Set the 357.Va net.inet.icmp.tstamprepl 358MIB variable to enable or disable 359.Dv ICMP_TSTAMPREPLY . 360.It Fl Q 361Somewhat quiet output. 362.No Don Ap t 363display ICMP error messages that are in response to our query messages. 364Originally, the 365.Fl v 366flag was required to display such errors, but 367.Fl v 368displays all ICMP error messages. 369On a busy machine, this output can be overbearing. 370Without the 371.Fl Q 372flag, 373.Nm 374prints out any ICMP error messages caused by its own ECHO_REQUEST 375messages. 376.It Fl R 377Record route. 378Includes the 379.Tn RECORD_ROUTE 380option in the 381.Tn ECHO_REQUEST 382packet and displays 383the route buffer on returned packets. 384Note that the IP header is only large enough for nine such routes; 385the 386.Xr traceroute 8 387command is usually better at determining the route packets take to a 388particular destination. 389If more routes come back than should, such as due to an illegal spoofed 390packet, ping will print the route list and then truncate it at the correct 391spot. 392Many hosts ignore or discard the 393.Tn RECORD_ROUTE 394option. 395.It Fl r 396Bypass the normal routing tables and send directly to a host on an attached 397network. 398If the host is not on a directly-attached network, an error is returned. 399This option can be used to ping a local host through an interface 400that has no route through it 401(e.g., after the interface was dropped by 402.Xr routed 8 ) . 403.It Fl T Ar ttl 404Set the IP Time To Live for multicasted packets. 405This flag only applies if the ping destination is a multicast address. 406.It Fl z Ar tos 407Use the specified type of service. 408.It Ar IPv4-host 409hostname or IPv4 address of the final destination node. 410.It Ar IPv4-mcast-group 411IPv4 multicast address of the final destination nodes. 412.El 413.Ss Options only for IPv6 targets 414.Bl -tag -width indent 415.It Fl 6 416Use IPv6 regardless of how the target is resolved. 417.It Fl b Ar bufsiz 418Set socket buffer size. 419.It Fl e Ar gateway 420Specifies to use 421.Ar gateway 422as the next hop to the destination. 423The gateway must be a neighbor of the sending node. 424.It Fl k Ar addrtype 425Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. 426.Ar addrtype 427must be a string constructed of the following characters. 428.Bl -tag -width Ds -compact 429.It Ic a 430requests unicast addresses from all of the responder's interfaces. 431If the character is omitted, 432only those addresses which belong to the interface which has the 433responder's address are requests. 434.It Ic c 435requests responder's IPv4-compatible and IPv4-mapped addresses. 436.It Ic g 437requests responder's global-scope addresses. 438.It Ic s 439requests responder's site-local addresses. 440.It Ic l 441requests responder's link-local addresses. 442.It Ic A 443requests responder's anycast addresses. 444Without this character, the responder will return unicast addresses only. 445With this character, the responder will return anycast addresses only. 446Note that the specification does not specify how to get responder's 447anycast addresses. 448This is an experimental option. 449.El 450.It Fl N 451Probe node information multicast group address 452.Pq Li ff02::2:ffxx:xxxx . 453.Ar host 454must be string hostname of the target 455(must not be a numeric IPv6 address). 456Node information multicast group will be computed based on given 457.Ar host , 458and will be used as the final destination. 459Since node information multicast group is a link-local multicast group, 460outgoing interface needs to be specified by 461.Fl I 462option. 463.Pp 464When specified twice, the address 465.Pq Li ff02::2:xxxx:xxxx 466is used instead. 467The former is in RFC 4620, the latter is in an old Internet Draft 468draft-ietf-ipngwg-icmp-name-lookup. 469Note that KAME-derived implementations including 470.Fx 471use the latter. 472.It Fl O 473Generate ICMPv6 Node Information supported query types query, 474rather than echo-request. 475.Fl s 476has no effect if 477.Fl O 478is specified. 479.It Fl u 480By default, 481.Nm 482asks the kernel to fragment packets to fit into the minimum IPv6 MTU. 483The 484.Fl u 485option 486will suppress the behavior in the following two levels: 487when the option is specified once, the behavior will be disabled for 488unicast packets. 489When the option is more than once, it will be disabled for both 490unicast and multicast packets. 491.It Fl Y 492Same as 493.Fl y , 494but with old packet format based on 03 draft. 495This option is present for backward compatibility. 496.Fl s 497has no effect if 498.Fl y 499is specified. 500.It Fl y 501Generate ICMPv6 Node Information DNS Name query, rather than echo-request. 502.Fl s 503has no effect if 504.Fl y 505is specified. 506.It Ar IPv6-hops 507IPv6 addresses for intermediate nodes, 508which will be put into type 0 routing header. 509.It Ar IPv6-host 510IPv6 address of the final destination node. 511.El 512.Ss Experimental options only for IPv6 target 513.Bl -tag -width indent 514.It Fl E 515Enables transport-mode IPsec encapsulated security payload. 516.It Fl Z 517Enables transport-mode IPsec authentication header. 518.El 519.Pp 520When using 521.Nm 522for fault isolation, it should first be run on the local host, to verify 523that the local network interface is up and running. 524Then, hosts and gateways further and further away should be 525.Dq pinged . 526Round-trip times and packet loss statistics are computed. 527If duplicate packets are received, they are not included in the packet 528loss calculation, although the round trip time of these packets is used 529in calculating the round-trip time statistics. 530When the specified number of packets have been sent 531(and received) 532or if the program is terminated with a 533.Dv SIGINT , 534a brief summary is displayed, showing the number of packets sent and 535received, and the minimum, mean, maximum, and standard deviation of 536the round-trip times. 537.Pp 538If 539.Nm 540receives a 541.Dv SIGINFO 542(see the 543.Cm status 544argument for 545.Xr stty 1 ) 546signal, the current number of packets sent and received, and the 547minimum, mean, maximum, and standard deviation of the round-trip times 548will be written to the standard output. 549.Pp 550This program is intended for use in network testing, measurement and 551management. 552Because of the load it can impose on the network, it is unwise to use 553.Nm 554during normal operations or from automated scripts. 555.Sh ICMP PACKET DETAILS 556An IP header without options is 20 bytes. 557An 558.Tn ICMP 559.Tn ECHO_REQUEST 560packet contains an additional 8 bytes worth of 561.Tn ICMP 562header followed by an arbitrary amount of data. 563When a 564.Ar packetsize 565is given, this indicated the size of this extra piece of data 566(the default is 56). 567Thus the amount of data received inside of an IP packet of type 568.Tn ICMP 569.Tn ECHO_REPLY 570will always be 8 bytes more than the requested data space 571(the 572.Tn ICMP 573header). 574.Pp 575If the data space is at least eight bytes large, 576.Nm 577uses the first eight bytes of this space to include a timestamp which 578it uses in the computation of round trip times. 579If less than eight bytes of pad are specified, no round trip times are 580given. 581.Sh DUPLICATE AND DAMAGED PACKETS 582The 583.Nm 584utility will report duplicate and damaged packets. 585Duplicate packets should never occur when pinging a unicast address, 586and seem to be caused by 587inappropriate link-level retransmissions. 588Duplicates may occur in many situations and are rarely 589(if ever) 590a good sign, although the presence of low levels of duplicates may not 591always be cause for alarm. 592Duplicates are expected when pinging a broadcast or multicast address, 593since they are not really duplicates but replies from different hosts 594to the same request. 595.Pp 596Damaged packets are obviously serious cause for alarm and often 597indicate broken hardware somewhere in the 598.Nm 599packet's path (in the network or in the hosts). 600.Sh TRYING DIFFERENT DATA PATTERNS 601The 602(inter)network 603layer should never treat packets differently depending on the data 604contained in the data portion. 605Unfortunately, data-dependent problems have been known to sneak into 606networks and remain undetected for long periods of time. 607In many cases the particular pattern that will have problems is something 608that does not have sufficient 609.Dq transitions , 610such as all ones or all zeros, or a pattern right at the edge, such as 611almost all zeros. 612It is not 613necessarily enough to specify a data pattern of all zeros (for example) 614on the command line because the pattern that is of interest is 615at the data link level, and the relationship between what you type and 616what the controllers transmit can be complicated. 617.Pp 618This means that if you have a data-dependent problem you will probably 619have to do a lot of testing to find it. 620If you are lucky, you may manage to find a file that either 621cannot 622be sent across your network or that takes much longer to transfer than 623other similar length files. 624You can then examine this file for repeated patterns that you can test 625using the 626.Fl p 627option of 628.Nm . 629.Sh IPv4 TTL DETAILS 630The 631.Tn TTL 632value of an IP packet represents the maximum number of IP routers 633that the packet can go through before being thrown away. 634In current practice you can expect each router in the Internet to decrement 635the 636.Tn TTL 637field by exactly one. 638.Pp 639The 640.Tn TCP/IP 641specification recommends setting the 642.Tn TTL 643field for 644.Tn IP 645packets to 64, but many systems use smaller values 646.No ( Bx 4.3 647uses 30, 648.Bx 4.2 649used 15). 650.Pp 651The maximum possible value of this field is 255, and most 652.Ux 653systems set 654the 655.Tn TTL 656field of 657.Tn ICMP ECHO_REQUEST 658packets to 255. 659This is why you will find you can 660.Dq ping 661some hosts, but not reach them with 662.Xr telnet 1 663or 664.Xr ftp 1 . 665.Pp 666In normal operation 667.Nm 668prints the ttl value from the packet it receives. 669When a remote system receives a ping packet, it can do one of three things 670with the 671.Tn TTL 672field in its response: 673.Bl -bullet 674.It 675Not change it; this is what 676.Bx 677systems did before the 678.Bx 4.3 tahoe 679release. 680In this case the 681.Tn TTL 682value in the received packet will be 255 minus the 683number of routers in the round-trip path. 684.It 685Set it to 255; this is what current 686.Bx 687systems do. 688In this case the 689.Tn TTL 690value in the received packet will be 255 minus the 691number of routers in the path 692.Em from 693the remote system 694.Em to 695the 696.Nm Ns Em ing 697host. 698.It 699Set it to some other value. 700Some machines use the same value for 701.Tn ICMP 702packets that they use for 703.Tn TCP 704packets, for example either 30 or 60. 705Others may use completely wild values. 706.El 707.Sh EXIT STATUS 708The 709.Nm 710utility exits with one of the following values: 711.Bl -tag -width indent 712.It 0 713At least one response was heard from the specified 714.Ar host . 715.It 2 716The transmission was successful but no responses were received. 717.It any other value 718An error occurred. 719.El 720.Sh EXAMPLES 721The following will send ICMPv6 echo request to 722.Li dst.foo.com . 723.Bd -literal -offset indent 724ping -6 -n dst.foo.com 725.Ed 726.Pp 727The following will probe hostnames for all nodes on the network link attached to 728.Li wi0 729interface. 730The address 731.Li ff02::1 732is named the link-local all-node multicast address, and the packet would 733reach every node on the network link. 734.Bd -literal -offset indent 735ping -6 -y ff02::1%wi0 736.Ed 737.Pp 738The following will probe addresses assigned to the destination node, 739.Li dst.foo.com . 740.Bd -literal -offset indent 741ping -6 -k agl dst.foo.com 742.Ed 743.Sh SEE ALSO 744.Xr netstat 1 , 745.Xr icmp 4 , 746.Xr icmp6 4 , 747.Xr inet6 4 , 748.Xr ip6 4 , 749.Xr ifconfig 8 , 750.Xr routed 8 , 751.Xr traceroute 8 752.Xr traceroute6 8 753.Rs 754.%A A. Conta 755.%A S. Deering 756.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification" 757.%N RFC 2463 758.%D December 1998 759.Re 760.Rs 761.%A Matt Crawford 762.%T "IPv6 Node Information Queries" 763.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt 764.%D May 2002 765.%O work in progress material 766.Re 767.Sh HISTORY 768The 769.Nm 770utility appeared in 771.Bx 4.3 . 772The 773.Nm ping6 774utility with IPv6 support first appeared in the WIDE Hydrangea IPv6 775protocol stack kit. 776.Pp 777IPv6 and IPsec support based on the KAME Project 778.Pq Pa http://www.kame.net/ 779stack was initially integrated into 780.Fx 4.0 . 781.Pp 782The 783.Nm ping6 784utility was merged to 785.Nm 786in Google Summer of Code 2019. 787.Sh AUTHORS 788The original 789.Nm 790utility was written by 791.An Mike Muuss 792while at the US Army Ballistics 793Research Laboratory. 794.Sh BUGS 795Many Hosts and Gateways ignore the IPv4 796.Tn RECORD_ROUTE 797option. 798.Pp 799The maximum IP header length is too small for options like 800.Tn RECORD_ROUTE 801to be completely useful. 802.No There Ap s 803not much that can be done about this, however. 804.Pp 805Flood pinging is not recommended in general, and flood pinging the 806broadcast address should only be done under very controlled conditions. 807.Pp 808The 809.Fl v 810option is not worth much on busy hosts. 811