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.\" 30.Dd September 15, 2023 31.Dt PING 8 32.Os 33.Sh NAME 34.Nm ping 35.Nd send 36ICMP 37or 38ICMPv6 ECHO_REQUEST 39packets to network hosts 40.Sh SYNOPSIS 41.Nm 42.Op Fl 4AaDdfHnoQqRrv 43.Op Fl .\& Ns Ar chars 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 .\& Ns Ar chars 64.Op Fl C Ar pcp 65.Op Fl c Ar count 66.Op Fl I Ar iface 67.Op Fl i Ar wait 68.Op Fl l Ar preload 69.Op Fl M Cm mask | time 70.Op Fl m Ar ttl 71.Op Fl P Ar policy 72.Op Fl p Ar pattern 73.Op Fl S Ar src_addr 74.Op Fl s Ar packetsize 75.Op Fl T Ar ttl 76.Op Fl t Ar timeout 77.Op Fl W Ar waittime 78.Op Fl z Ar tos 79.Ar IPv4-mcast-group 80.Nm 81.Op Fl 6AaDdEfHNnOoquvYyZ 82.Op Fl .\& Ns Ar chars 83.Op Fl b Ar bufsiz 84.Op Fl C Ar pcp 85.Op Fl c Ar count 86.Op Fl e Ar gateway 87.Op Fl I Ar interface 88.Op Fl i Ar wait 89.Op Fl k Ar addrtype 90.Op Fl l Ar preload 91.Op Fl m Ar hoplimit 92.Op Fl P Ar policy 93.Op Fl p Ar pattern 94.Op Fl S Ar sourceaddr 95.Op Fl s Ar packetsize 96.Op Fl t Ar timeout 97.Op Fl W Ar waittime 98.Op Ar IPv6-hops ... 99.Ar IPv6-host 100.Sh DESCRIPTION 101The 102.Nm 103utility invoked with an IPv4 target 104.Ar ( IPv4-host 105or 106.Ar IPv4-mcast-group ) 107uses the 108ICMP 109.No protocol Ap s mandatory 110ECHO_REQUEST 111datagram to elicit an 112ICMP ECHO_RESPONSE 113from a host or gateway. 114ECHO_REQUEST 115datagrams 116.Pq Dq pings 117have an IP and 118ICMP 119header, followed by a 120.Dq struct timeval 121and then an arbitrary number of 122.Dq pad 123bytes used to fill out the packet. 124.Pp 125When invoked with an IPv6 target 126.Ar ( IPv6-host ) , 127it uses the 128ICMPv6 129protocol's mandatory 130ICMP6_ECHO_REQUEST 131datagram to elicit an 132ICMP6_ECHO_REPLY. 133ICMP6_ECHO_REQUEST 134datagrams have an IPv6 header and 135ICMPv6 136header formatted as documented in RFC 2463. 137.Pp 138When invoked with a hostname, the version to which the target is resolved first 139is used. 140In that case, the options and arguments used must be valid for the specific IP 141version, otherwise 142.Nm 143exits with an error. 144If the target is resolved to both IPv4 and IPv6, the specific IP version can be 145requested by 146.Fl 4 147or 148.Fl 6 149options, respectively. 150For backwards-compatibility, ICMPv6 can also be selected by invoking the binary 151as 152.Nm ping6 . 153.Ss Options common to both IPv4 and IPv6 targets 154.Bl -tag -width indent 155.It Fl .\& Ns Ar chars 156By default, for every 157ECHO_REQUEST 158sent, a period 159.Dq .\& 160is printed, while for every 161ECHO_REPLY 162received, a backspace is printed. 163This option takes an optional string argument listing characters 164that will be printed one by one in the provided order 165instead of the default period. 166.Pp 167Example usage: 168.Bd -literal -offset indent 169ping -.0123456789 freebsd.org 170.Ed 171.It Fl A 172Audible. 173Output a bell 174(ASCII 1750x07) 176character when no packet is received before the next packet 177is transmitted. 178To cater for round-trip times that are longer than the interval 179between transmissions, further missing packets cause a bell only 180if the maximum number of unreceived packets has increased. 181.It Fl a 182Audible. 183Include a bell 184(ASCII 1850x07) 186character in the output when any packet is received. 187.It Fl C Ar pcp 188Add an 802.1p Ethernet Priority Code Point when sending a packet. 1890..7 uses that specific PCP, -1 uses the interface default PCP (or none). 190.It Fl c Ar count 191Stop after sending 192(and receiving) 193.Ar count 194ECHO_RESPONSE 195packets. 196If this option is not specified, 197.Nm 198will operate until interrupted. 199.Pp 200For an IPv4 target, if this option is specified in conjunction with ping sweeps, 201each sweep will consist of 202.Ar count 203packets. 204.It Fl D 205Disable fragmentation. 206.It Fl d 207Set the 208.Dv SO_DEBUG 209option on the socket being used. 210.It Fl f 211Flood ping. 212Outputs packets as fast as they come back or one hundred times per second, 213whichever is more. 214Implies 215.Fl .\& 216to print a period for every 217ECHO_REQUEST 218sent and a backspace for every 219ECHO_REPLY 220received. 221This provides a rapid display of how many packets are being dropped. 222Only the super-user may use this option. 223.Bf -emphasis 224This can be very hard on a network and should be used with caution. 225.Ef 226.It Fl H 227Hostname output. 228Try to do a reverse DNS lookup when displaying addresses. 229This is the opposite of the 230.Fl n 231option. 232.It Fl I Ar iface 233For an IPv4 target, 234.Ar iface 235is an IP address indentifying an interface from which the packets will be sent. 236This flag applies only if the ping target is a multicast address. 237.Pp 238For an IPv6 target, 239.Ar iface 240is a name of an interface (e.g., `em0') from which the packets will be sent. 241This flag applies if the ping target is a multicast address, or 242link-local/site-local unicast address. 243.It Fl i Ar wait 244Wait 245.Ar wait 246seconds 247.Em between sending each packet . 248The default is to wait for one second between each packet. 249The wait time may be fractional, but only the super-user may specify 250values less than 1 second. 251This option is incompatible with the 252.Fl f 253option. 254.It Fl l Ar preload 255If 256.Ar preload 257is specified, 258.Nm 259sends that many packets as fast as possible before falling into its normal 260mode of behavior. 261Only the super-user may use this option. 262.It Fl m Ar ttl 263For an IPv4 target, set the IP Time To Live for outgoing packets. 264If not specified, the kernel uses the value of the 265.Va net.inet.ip.ttl 266MIB variable. 267.Pp 268For an IPv6 target, set the IPv6 hoplimit. 269.It Fl n 270Numeric output only. 271No attempt will be made to lookup symbolic names for host addresses. 272This is the opposite of 273.Fl H , 274and it is the default behavior. 275.It Fl o 276Exit successfully after receiving one reply packet. 277.It Fl P Ar policy 278.Ar policy 279specifies IPsec policy for the ping session. 280For details please refer to 281.Xr ipsec 4 282and 283.Xr ipsec_set_policy 3 . 284.It Fl p Ar pattern 285You may specify up to 16 286.Dq pad 287bytes to fill out the packet you send. 288This is useful for diagnosing data-dependent problems in a network. 289For example, 290.Dq Li \-p ff 291will cause the sent packet to be filled with all 292ones. 293.It Fl q 294Quiet output. 295Nothing is displayed except the summary lines at startup time and 296when finished. 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. 302.Pp 303For IPv4, if the IP address is not one of this machine's interface 304addresses, an error is returned and nothing is sent. 305.Pp 306For IPv6, the source address must be one of the unicast addresses of 307the sending node, and must be numeric. 308.It Fl s Ar packetsize 309Specify the number of data bytes to be sent. 310The default is 56, which translates into 64 311ICMP 312data bytes when combined 313with the 8 bytes of 314ICMP 315header data. 316.Pp 317For IPv4, only the super-user may specify values more than default. 318This option cannot be used with ping sweeps. 319.Pp 320For IPv6, you may need to specify 321.Fl b 322as well to extend socket buffer size. 323.It Fl t Ar timeout 324Specify a timeout, in seconds, before ping exits regardless of how 325many packets have been received. 326.It Fl v 327Verbose output. 328ICMP 329packets other than 330ECHO_RESPONSE 331that are received are listed. 332.It Fl W Ar waittime 333Time in milliseconds to wait for a reply for each packet sent. 334If a reply arrives later, the packet is not printed as replied, but 335considered as replied when calculating statistics. 336.El 337.Ss Options only for IPv4 targets 338.Bl -tag -width indent 339.It Fl 4 340Use IPv4 regardless of how the target is resolved. 341.It Fl G Ar sweepmaxsize 342Specify the maximum size of 343ICMP 344payload when sending sweeping pings. 345This option is required for ping sweeps. 346.It Fl g Ar sweepminsize 347Specify the size of 348ICMP 349payload to start with when sending sweeping pings. 350The default value is 0. 351.It Fl h Ar sweepincrsize 352Specify the number of bytes to increment the size of 353ICMP 354payload after 355each sweep when sending sweeping pings. 356The default value is 1. 357.It Fl L 358Suppress loopback of multicast packets. 359This flag only applies if the ping destination is a multicast address. 360.It Fl M Cm mask | time 361Use 362.Dv ICMP_MASKREQ 363or 364.Dv ICMP_TSTAMP 365instead of 366.Dv ICMP_ECHO . 367For 368.Cm mask , 369print the netmask of the remote machine. 370Set the 371.Va net.inet.icmp.maskrepl 372MIB variable to enable 373.Dv ICMP_MASKREPLY 374and 375.Va net.inet.icmp.maskfake 376if you want to override the netmask in the response. 377For 378.Cm time , 379print the origination, reception and transmission timestamps. 380Set the 381.Va net.inet.icmp.tstamprepl 382MIB variable to enable or disable 383.Dv ICMP_TSTAMPREPLY . 384.It Fl Q 385Somewhat quiet output. 386.No Don Ap t 387display ICMP error messages that are in response to our query messages. 388Originally, the 389.Fl v 390flag was required to display such errors, but 391.Fl v 392displays all ICMP error messages. 393On a busy machine, this output can be overbearing. 394Without the 395.Fl Q 396flag, 397.Nm 398prints out any ICMP error messages caused by its own ECHO_REQUEST 399messages. 400.It Fl R 401Record route. 402Includes the 403RECORD_ROUTE 404option in the 405ECHO_REQUEST 406packet and displays 407the route buffer on returned packets. 408Note that the IP header is only large enough for nine such routes; 409the 410.Xr traceroute 8 411command is usually better at determining the route packets take to a 412particular destination. 413If more routes come back than should, such as due to an illegal spoofed 414packet, ping will print the route list and then truncate it at the correct 415spot. 416Many hosts ignore or discard the 417RECORD_ROUTE 418option. 419.It Fl r 420Bypass the normal routing tables and send directly to a host on an attached 421network. 422If the host is not on a directly-attached network, an error is returned. 423This option can be used to ping a local host through an interface 424that has no route through it 425(e.g., after the interface was dropped by 426.Xr routed 8 ) . 427.It Fl T Ar ttl 428Set the IP Time To Live for multicasted packets. 429This flag only applies if the ping destination is a multicast address. 430.It Fl z Ar tos 431Use the specified type of service. 432.It Ar IPv4-host 433hostname or IPv4 address of the final destination node. 434.It Ar IPv4-mcast-group 435IPv4 multicast address of the final destination nodes. 436.El 437.Ss Options only for IPv6 targets 438.Bl -tag -width indent 439.It Fl 6 440Use IPv6 regardless of how the target is resolved. 441.It Fl b Ar bufsiz 442Set socket buffer size. 443.It Fl e Ar gateway 444Specifies to use 445.Ar gateway 446as the next hop to the destination. 447The gateway must be a neighbor of the sending node. 448.It Fl k Ar addrtype 449Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. 450.Ar addrtype 451must be a string constructed of the following characters. 452.Bl -tag -width Ds -compact 453.It Ic a 454requests unicast addresses from all of the responder's interfaces. 455If the character is omitted, 456only those addresses which belong to the interface which has the 457responder's address are requests. 458.It Ic c 459requests responder's IPv4-compatible and IPv4-mapped addresses. 460.It Ic g 461requests responder's global-scope addresses. 462.It Ic s 463requests responder's site-local addresses. 464.It Ic l 465requests responder's link-local addresses. 466.It Ic A 467requests responder's anycast addresses. 468Without this character, the responder will return unicast addresses only. 469With this character, the responder will return anycast addresses only. 470Note that the specification does not specify how to get responder's 471anycast addresses. 472This is an experimental option. 473.El 474.It Fl N 475Probe node information multicast group address 476.Pq Li ff02::2:ffxx:xxxx . 477.Ar host 478must be string hostname of the target 479(must not be a numeric IPv6 address). 480Node information multicast group will be computed based on given 481.Ar host , 482and will be used as the final destination. 483Since node information multicast group is a link-local multicast group, 484outgoing interface needs to be specified by 485.Fl I 486option. 487.Pp 488When specified twice, the address 489.Pq Li ff02::2:xxxx:xxxx 490is used instead. 491The former is in RFC 4620, the latter is in an old Internet Draft 492draft-ietf-ipngwg-icmp-name-lookup. 493Note that KAME-derived implementations including 494.Fx 495use the latter. 496.It Fl O 497Generate ICMPv6 Node Information supported query types query, 498rather than echo-request. 499.Fl s 500has no effect if 501.Fl O 502is specified. 503.It Fl u 504By default, 505.Nm 506asks the kernel to fragment packets to fit into the minimum IPv6 MTU. 507The 508.Fl u 509option 510will suppress the behavior in the following two levels: 511when the option is specified once, the behavior will be disabled for 512unicast packets. 513When the option is more than once, it will be disabled for both 514unicast and multicast packets. 515.It Fl Y 516Same as 517.Fl y , 518but with old packet format based on 03 draft. 519This option is present for backward compatibility. 520.Fl s 521has no effect if 522.Fl y 523is specified. 524.It Fl y 525Generate ICMPv6 Node Information DNS Name query, rather than echo-request. 526.Fl s 527has no effect if 528.Fl y 529is specified. 530.It Ar IPv6-hops 531IPv6 addresses for intermediate nodes, 532which will be put into type 0 routing header. 533.It Ar IPv6-host 534IPv6 address of the final destination node. 535.El 536.Ss Experimental options only for IPv6 target 537.Bl -tag -width indent 538.It Fl E 539Enables transport-mode IPsec encapsulated security payload. 540.It Fl Z 541Enables transport-mode IPsec authentication header. 542.El 543.Pp 544When using 545.Nm 546for fault isolation, it should first be run on the local host, to verify 547that the local network interface is up and running. 548Then, hosts and gateways further and further away should be 549.Dq pinged . 550Round-trip times and packet loss statistics are computed. 551If duplicate packets are received, they are not included in the packet 552loss calculation, although the round trip time of these packets is used 553in calculating the round-trip time statistics. 554When the specified number of packets have been sent 555(and received) 556or if the program is terminated with a 557.Dv SIGINT , 558a brief summary is displayed, showing the number of packets sent and 559received, and the minimum, mean, maximum, and standard deviation of 560the round-trip times. 561.Pp 562If 563.Nm 564receives a 565.Dv SIGINFO 566(see the 567.Cm status 568argument for 569.Xr stty 1 ) 570signal, the current number of packets sent and received, and the 571minimum, mean, maximum, and standard deviation of the round-trip times 572will be written to the standard output. 573.Pp 574This program is intended for use in network testing, measurement and 575management. 576Because of the load it can impose on the network, it is unwise to use 577.Nm 578during normal operations or from automated scripts. 579.Sh ICMP PACKET DETAILS 580An IP header without options is 20 bytes. 581An 582ICMP 583ECHO_REQUEST 584packet contains an additional 8 bytes worth of 585ICMP 586header followed by an arbitrary amount of data. 587When a 588.Ar packetsize 589is given, this indicated the size of this extra piece of data 590(the default is 56). 591Thus the amount of data received inside of an IP packet of type 592ICMP 593ECHO_REPLY 594will always be 8 bytes more than the requested data space 595(the 596ICMP 597header). 598.Pp 599If the data space is at least eight bytes large, 600.Nm 601uses the first eight bytes of this space to include a timestamp which 602it uses in the computation of round trip times. 603If less than eight bytes of pad are specified, no round trip times are 604given. 605.Sh DUPLICATE AND DAMAGED PACKETS 606The 607.Nm 608utility will report duplicate and damaged packets. 609Duplicate packets should never occur when pinging a unicast address, 610and seem to be caused by 611inappropriate link-level retransmissions. 612Duplicates may occur in many situations and are rarely 613(if ever) 614a good sign, although the presence of low levels of duplicates may not 615always be cause for alarm. 616Duplicates are expected when pinging a broadcast or multicast address, 617since they are not really duplicates but replies from different hosts 618to the same request. 619.Pp 620Damaged packets are obviously serious cause for alarm and often 621indicate broken hardware somewhere in the 622.Nm 623packet's path (in the network or in the hosts). 624.Sh TRYING DIFFERENT DATA PATTERNS 625The 626(inter)network 627layer should never treat packets differently depending on the data 628contained in the data portion. 629Unfortunately, data-dependent problems have been known to sneak into 630networks and remain undetected for long periods of time. 631In many cases the particular pattern that will have problems is something 632that does not have sufficient 633.Dq transitions , 634such as all ones or all zeros, or a pattern right at the edge, such as 635almost all zeros. 636It is not 637necessarily enough to specify a data pattern of all zeros (for example) 638on the command line because the pattern that is of interest is 639at the data link level, and the relationship between what you type and 640what the controllers transmit can be complicated. 641.Pp 642This means that if you have a data-dependent problem you will probably 643have to do a lot of testing to find it. 644If you are lucky, you may manage to find a file that either 645cannot 646be sent across your network or that takes much longer to transfer than 647other similar length files. 648You can then examine this file for repeated patterns that you can test 649using the 650.Fl p 651option of 652.Nm . 653.Sh IPv4 TTL DETAILS 654The 655TTL 656value of an IP packet represents the maximum number of IP routers 657that the packet can go through before being thrown away. 658In current practice you can expect each router in the Internet to decrement 659the 660TTL 661field by exactly one. 662.Pp 663The 664TCP/IP 665specification recommends setting the 666TTL 667field for 668IP 669packets to 64. 670.Pp 671The maximum possible value of this field is 255, and some 672.Ux 673systems set 674the 675TTL 676field of 677ICMP ECHO_REQUEST 678packets to 255. 679This is why you will find you can 680.Dq ping 681some hosts, but not reach them with 682.Xr telnet 1 683or 684.Xr ftp 1 . 685.Pp 686In normal operation 687.Nm 688prints the ttl value from the packet it receives. 689When a remote system receives a ping packet, it can do one of three things 690with the 691TTL 692field in its response: 693.Bl -bullet 694.It 695Not change it; this is what 696.Bx 697systems did before the 698.Bx 4.3 tahoe 699release. 700In this case the 701TTL 702value in the received packet will be 255 minus the 703number of routers in the round-trip path. 704.It 705Set it to 64; this is what current 706.Fx 707systems do. 708In this case the 709TTL 710value in the received packet will be 64 minus the 711number of routers in the path 712.Em from 713the remote system 714.Em to 715the 716.Nm Ns Em ing 717host. 718.It 719Set it to some other value. 720Some machines use the same value for 721ICMP 722packets that they use for 723TCP 724packets, for example either 30 or 60. 725Others may use completely wild values. 726.El 727.Sh EXIT STATUS 728The 729.Nm 730utility exits with one of the following values: 731.Bl -tag -width indent 732.It 0 733At least one response was heard from the specified 734.Ar host . 735.It 2 736The transmission was successful but no responses were received. 737.It any other value 738An error occurred. 739.El 740.Sh EXAMPLES 741The following will send ICMPv6 echo request to 742.Li dst.example.com . 743.Bd -literal -offset indent 744ping -6 -n dst.example.com 745.Ed 746.Pp 747The following will probe hostnames for all nodes on the network link attached to 748.Li wi0 749interface. 750The address 751.Li ff02::1 752is named the link-local all-node multicast address, and the packet would 753reach every node on the network link. 754.Bd -literal -offset indent 755ping -6 -y ff02::1%wi0 756.Ed 757.Pp 758The following will probe addresses assigned to the destination node, 759.Li dst.example.com . 760.Bd -literal -offset indent 761ping -6 -k agl dst.example.com 762.Ed 763.Sh SEE ALSO 764.Xr netstat 1 , 765.Xr icmp 4 , 766.Xr icmp6 4 , 767.Xr inet6 4 , 768.Xr ip6 4 , 769.Xr ifconfig 8 , 770.Xr routed 8 , 771.Xr traceroute 8 , 772.Xr traceroute6 8 773.Rs 774.%A A. Conta 775.%A S. Deering 776.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification" 777.%N RFC 2463 778.%D December 1998 779.Re 780.Rs 781.%A Matt Crawford 782.%T "IPv6 Node Information Queries" 783.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt 784.%D May 2002 785.%O work in progress material 786.Re 787.Sh HISTORY 788The 789.Nm 790utility appeared in 791.Bx 4.3 . 792The 793.Nm ping6 794utility with IPv6 support first appeared in the WIDE Hydrangea IPv6 795protocol stack kit. 796.Pp 797IPv6 and IPsec support based on the KAME Project 798.Pq Pa https://www.kame.net/ 799stack was initially integrated into 800.Fx 4.0 . 801.Pp 802The 803.Nm ping6 804utility was merged to 805.Nm 806in Google Summer of Code 2019. 807.Sh AUTHORS 808The original 809.Nm 810utility was written by 811.An Mike Muuss 812while at the US Army Ballistics 813Research Laboratory. 814.Sh BUGS 815Many Hosts and Gateways ignore the IPv4 816RECORD_ROUTE 817option. 818.Pp 819The maximum IP header length is too small for options like 820RECORD_ROUTE 821to be completely useful. 822.No There Ap s 823not much that can be done about this, however. 824.Pp 825Flood pinging is not recommended in general, and flood pinging the 826broadcast address should only be done under very controlled conditions. 827.Pp 828The 829.Fl v 830option is not worth much on busy hosts. 831