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 November 20, 2022 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 count 85.Op Fl e Ar gateway 86.Op Fl I Ar interface 87.Op Fl i Ar wait 88.Op Fl k Ar addrtype 89.Op Fl l Ar preload 90.Op Fl m Ar hoplimit 91.Op Fl P Ar policy 92.Op Fl p Ar pattern 93.Op Fl S Ar sourceaddr 94.Op Fl s Ar packetsize 95.Op Fl t Ar timeout 96.Op Fl W Ar waittime 97.Op Ar IPv6-hops ... 98.Ar IPv6-host 99.Sh DESCRIPTION 100The 101.Nm 102utility invoked with an IPv4 target 103.Ar ( IPv4-host 104or 105.Ar IPv4-mcast-group ) 106uses the 107ICMP 108.No protocol Ap s mandatory 109ECHO_REQUEST 110datagram to elicit an 111ICMP ECHO_RESPONSE 112from a host or gateway. 113ECHO_REQUEST 114datagrams 115.Pq Dq pings 116have an IP and 117ICMP 118header, followed by a 119.Dq struct timeval 120and then an arbitrary number of 121.Dq pad 122bytes used to fill out the packet. 123.Pp 124When invoked with an IPv6 target 125.Ar ( IPv6-host ) , 126it uses the 127ICMPv6 128protocol's mandatory 129ICMP6_ECHO_REQUEST 130datagram to elicit an 131ICMP6_ECHO_REPLY. 132ICMP6_ECHO_REQUEST 133datagrams have an IPv6 header and 134ICMPv6 135header formatted as documented in RFC 2463. 136.Pp 137When invoked with a hostname, the version to which the target is resolved first 138is used. 139In that case, the options and arguments used must be valid for the specific IP 140version, otherwise 141.Nm 142exits with an error. 143If the target is resolved to both IPv4 and IPv6, the specific IP version can be 144requested by 145.Fl 4 146or 147.Fl 6 148options, respectively. 149For backwards-compatibility, ICMPv6 can also be selected by invoking the binary 150as 151.Nm ping6 . 152.Ss Options common to both IPv4 and IPv6 targets 153.Bl -tag -width indent 154.It Fl .\& Ns Ar chars 155By default, for every 156ECHO_REQUEST 157sent, a period 158.Dq .\& 159is printed, while for every 160ECHO_REPLY 161received, a backspace is printed. 162This option takes an optional string argument listing characters 163that will be printed one by one in the provided order 164instead of the default period. 165.Pp 166Example usage: 167.Bd -literal -offset indent 168ping -.0123456789 freebsd.org 169.Ed 170.It Fl A 171Audible. 172Output a bell 173(ASCII 1740x07) 175character when no packet is received before the next packet 176is transmitted. 177To cater for round-trip times that are longer than the interval 178between transmissions, further missing packets cause a bell only 179if the maximum number of unreceived packets has increased. 180.It Fl a 181Audible. 182Include a bell 183(ASCII 1840x07) 185character in the output when any packet is received. 186.It Fl C Ar pcp 187Add an 802.1p Ethernet Priority Code Point when sending a packet. 1880..7 uses that specific PCP, -1 uses the interface default PCP (or none). 189.It Fl c Ar count 190Stop after sending 191(and receiving) 192.Ar count 193ECHO_RESPONSE 194packets. 195If this option is not specified, 196.Nm 197will operate until interrupted. 198.Pp 199For an IPv4 target, if this option is specified in conjunction with ping sweeps, 200each sweep will consist of 201.Ar count 202packets. 203.It Fl D 204Disable fragmentation. 205.It Fl d 206Set the 207.Dv SO_DEBUG 208option on the socket being used. 209.It Fl f 210Flood ping. 211Outputs packets as fast as they come back or one hundred times per second, 212whichever is more. 213Implies 214.Fl .\& 215to print a period for every 216ECHO_REQUEST 217sent and a backspace for every 218ECHO_REPLY 219received. 220This provides a rapid display of how many packets are being dropped. 221Only the super-user may use this option. 222.Bf -emphasis 223This can be very hard on a network and should be used with caution. 224.Ef 225.It Fl H 226Hostname output. 227Try to do a reverse DNS lookup when displaying addresses. 228This is the opposite of the 229.Fl n 230option. 231.It Fl I Ar iface 232For an IPv4 target, 233.Ar iface 234is an IP address indentifying an interface from which the packets will be sent. 235This flag applies only if the ping target is a multicast address. 236.Pp 237For an IPv6 target, 238.Ar iface 239is a name of an interface (e.g., `em0') from which the packets will be sent. 240This flag applies if the ping target is a multicast address, or 241link-local/site-local unicast address. 242.It Fl i Ar wait 243Wait 244.Ar wait 245seconds 246.Em between sending each packet . 247The default is to wait for one second between each packet. 248The wait time may be fractional, but only the super-user may specify 249values less than 1 second. 250This option is incompatible with the 251.Fl f 252option. 253.It Fl l Ar preload 254If 255.Ar preload 256is specified, 257.Nm 258sends that many packets as fast as possible before falling into its normal 259mode of behavior. 260Only the super-user may use this option. 261.It Fl m Ar ttl 262For an IPv4 target, set the IP Time To Live for outgoing packets. 263If not specified, the kernel uses the value of the 264.Va net.inet.ip.ttl 265MIB variable. 266.Pp 267For an IPv6 target, set the IPv6 hoplimit. 268.It Fl n 269Numeric output only. 270No attempt will be made to lookup symbolic names for host addresses. 271This is the opposite of 272.Fl H , 273and it is the default behavior. 274.It Fl o 275Exit successfully after receiving one reply packet. 276.It Fl P Ar policy 277.Ar policy 278specifies IPsec policy for the ping session. 279For details please refer to 280.Xr ipsec 4 281and 282.Xr ipsec_set_policy 3 . 283.It Fl p Ar pattern 284You may specify up to 16 285.Dq pad 286bytes to fill out the packet you send. 287This is useful for diagnosing data-dependent problems in a network. 288For example, 289.Dq Li \-p ff 290will cause the sent packet to be filled with all 291ones. 292.It Fl q 293Quiet output. 294Nothing is displayed except the summary lines at startup time and 295when finished. 296.It Fl S Ar src_addr 297Use the following IP address as the source address in outgoing packets. 298On hosts with more than one IP address, this option can be used to 299force the source address to be something other than the IP address 300of the interface the probe packet is sent on. 301.Pp 302For IPv4, if the IP address is not one of this machine's interface 303addresses, an error is returned and nothing is sent. 304.Pp 305For IPv6, the source address must be one of the unicast addresses of 306the sending node, and must be numeric. 307.It Fl s Ar packetsize 308Specify the number of data bytes to be sent. 309The default is 56, which translates into 64 310ICMP 311data bytes when combined 312with the 8 bytes of 313ICMP 314header data. 315.Pp 316For IPv4, only the super-user may specify values more than default. 317This option cannot be used with ping sweeps. 318.Pp 319For IPv6, you may need to specify 320.Fl b 321as well to extend socket buffer size. 322.It Fl t Ar timeout 323Specify a timeout, in seconds, before ping exits regardless of how 324many packets have been received. 325.It Fl v 326Verbose output. 327ICMP 328packets other than 329ECHO_RESPONSE 330that are received are listed. 331.It Fl W Ar waittime 332Time in milliseconds to wait for a reply for each packet sent. 333If a reply arrives later, the packet is not printed as replied, but 334considered as replied when calculating statistics. 335.El 336.Ss Options only for IPv4 targets 337.Bl -tag -width indent 338.It Fl 4 339Use IPv4 regardless of how the target is resolved. 340.It Fl G Ar sweepmaxsize 341Specify the maximum size of 342ICMP 343payload when sending sweeping pings. 344This option is required for ping sweeps. 345.It Fl g Ar sweepminsize 346Specify the size of 347ICMP 348payload to start with when sending sweeping pings. 349The default value is 0. 350.It Fl h Ar sweepincrsize 351Specify the number of bytes to increment the size of 352ICMP 353payload after 354each sweep when sending sweeping pings. 355The default value is 1. 356.It Fl L 357Suppress loopback of multicast packets. 358This flag only applies if the ping destination is a multicast address. 359.It Fl M Cm mask | time 360Use 361.Dv ICMP_MASKREQ 362or 363.Dv ICMP_TSTAMP 364instead of 365.Dv ICMP_ECHO . 366For 367.Cm mask , 368print the netmask of the remote machine. 369Set the 370.Va net.inet.icmp.maskrepl 371MIB variable to enable 372.Dv ICMP_MASKREPLY 373and 374.Va net.inet.icmp.maskfake 375if you want to override the netmask in the response. 376For 377.Cm time , 378print the origination, reception and transmission timestamps. 379Set the 380.Va net.inet.icmp.tstamprepl 381MIB variable to enable or disable 382.Dv ICMP_TSTAMPREPLY . 383.It Fl Q 384Somewhat quiet output. 385.No Don Ap t 386display ICMP error messages that are in response to our query messages. 387Originally, the 388.Fl v 389flag was required to display such errors, but 390.Fl v 391displays all ICMP error messages. 392On a busy machine, this output can be overbearing. 393Without the 394.Fl Q 395flag, 396.Nm 397prints out any ICMP error messages caused by its own ECHO_REQUEST 398messages. 399.It Fl R 400Record route. 401Includes the 402RECORD_ROUTE 403option in the 404ECHO_REQUEST 405packet and displays 406the route buffer on returned packets. 407Note that the IP header is only large enough for nine such routes; 408the 409.Xr traceroute 8 410command is usually better at determining the route packets take to a 411particular destination. 412If more routes come back than should, such as due to an illegal spoofed 413packet, ping will print the route list and then truncate it at the correct 414spot. 415Many hosts ignore or discard the 416RECORD_ROUTE 417option. 418.It Fl r 419Bypass the normal routing tables and send directly to a host on an attached 420network. 421If the host is not on a directly-attached network, an error is returned. 422This option can be used to ping a local host through an interface 423that has no route through it 424(e.g., after the interface was dropped by 425.Xr routed 8 ) . 426.It Fl T Ar ttl 427Set the IP Time To Live for multicasted packets. 428This flag only applies if the ping destination is a multicast address. 429.It Fl z Ar tos 430Use the specified type of service. 431.It Ar IPv4-host 432hostname or IPv4 address of the final destination node. 433.It Ar IPv4-mcast-group 434IPv4 multicast address of the final destination nodes. 435.El 436.Ss Options only for IPv6 targets 437.Bl -tag -width indent 438.It Fl 6 439Use IPv6 regardless of how the target is resolved. 440.It Fl b Ar bufsiz 441Set socket buffer size. 442.It Fl e Ar gateway 443Specifies to use 444.Ar gateway 445as the next hop to the destination. 446The gateway must be a neighbor of the sending node. 447.It Fl k Ar addrtype 448Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. 449.Ar addrtype 450must be a string constructed of the following characters. 451.Bl -tag -width Ds -compact 452.It Ic a 453requests unicast addresses from all of the responder's interfaces. 454If the character is omitted, 455only those addresses which belong to the interface which has the 456responder's address are requests. 457.It Ic c 458requests responder's IPv4-compatible and IPv4-mapped addresses. 459.It Ic g 460requests responder's global-scope addresses. 461.It Ic s 462requests responder's site-local addresses. 463.It Ic l 464requests responder's link-local addresses. 465.It Ic A 466requests responder's anycast addresses. 467Without this character, the responder will return unicast addresses only. 468With this character, the responder will return anycast addresses only. 469Note that the specification does not specify how to get responder's 470anycast addresses. 471This is an experimental option. 472.El 473.It Fl N 474Probe node information multicast group address 475.Pq Li ff02::2:ffxx:xxxx . 476.Ar host 477must be string hostname of the target 478(must not be a numeric IPv6 address). 479Node information multicast group will be computed based on given 480.Ar host , 481and will be used as the final destination. 482Since node information multicast group is a link-local multicast group, 483outgoing interface needs to be specified by 484.Fl I 485option. 486.Pp 487When specified twice, the address 488.Pq Li ff02::2:xxxx:xxxx 489is used instead. 490The former is in RFC 4620, the latter is in an old Internet Draft 491draft-ietf-ipngwg-icmp-name-lookup. 492Note that KAME-derived implementations including 493.Fx 494use the latter. 495.It Fl O 496Generate ICMPv6 Node Information supported query types query, 497rather than echo-request. 498.Fl s 499has no effect if 500.Fl O 501is specified. 502.It Fl u 503By default, 504.Nm 505asks the kernel to fragment packets to fit into the minimum IPv6 MTU. 506The 507.Fl u 508option 509will suppress the behavior in the following two levels: 510when the option is specified once, the behavior will be disabled for 511unicast packets. 512When the option is more than once, it will be disabled for both 513unicast and multicast packets. 514.It Fl Y 515Same as 516.Fl y , 517but with old packet format based on 03 draft. 518This option is present for backward compatibility. 519.Fl s 520has no effect if 521.Fl y 522is specified. 523.It Fl y 524Generate ICMPv6 Node Information DNS Name query, rather than echo-request. 525.Fl s 526has no effect if 527.Fl y 528is specified. 529.It Ar IPv6-hops 530IPv6 addresses for intermediate nodes, 531which will be put into type 0 routing header. 532.It Ar IPv6-host 533IPv6 address of the final destination node. 534.El 535.Ss Experimental options only for IPv6 target 536.Bl -tag -width indent 537.It Fl E 538Enables transport-mode IPsec encapsulated security payload. 539.It Fl Z 540Enables transport-mode IPsec authentication header. 541.El 542.Pp 543When using 544.Nm 545for fault isolation, it should first be run on the local host, to verify 546that the local network interface is up and running. 547Then, hosts and gateways further and further away should be 548.Dq pinged . 549Round-trip times and packet loss statistics are computed. 550If duplicate packets are received, they are not included in the packet 551loss calculation, although the round trip time of these packets is used 552in calculating the round-trip time statistics. 553When the specified number of packets have been sent 554(and received) 555or if the program is terminated with a 556.Dv SIGINT , 557a brief summary is displayed, showing the number of packets sent and 558received, and the minimum, mean, maximum, and standard deviation of 559the round-trip times. 560.Pp 561If 562.Nm 563receives a 564.Dv SIGINFO 565(see the 566.Cm status 567argument for 568.Xr stty 1 ) 569signal, the current number of packets sent and received, and the 570minimum, mean, maximum, and standard deviation of the round-trip times 571will be written to the standard output. 572.Pp 573This program is intended for use in network testing, measurement and 574management. 575Because of the load it can impose on the network, it is unwise to use 576.Nm 577during normal operations or from automated scripts. 578.Sh ICMP PACKET DETAILS 579An IP header without options is 20 bytes. 580An 581ICMP 582ECHO_REQUEST 583packet contains an additional 8 bytes worth of 584ICMP 585header followed by an arbitrary amount of data. 586When a 587.Ar packetsize 588is given, this indicated the size of this extra piece of data 589(the default is 56). 590Thus the amount of data received inside of an IP packet of type 591ICMP 592ECHO_REPLY 593will always be 8 bytes more than the requested data space 594(the 595ICMP 596header). 597.Pp 598If the data space is at least eight bytes large, 599.Nm 600uses the first eight bytes of this space to include a timestamp which 601it uses in the computation of round trip times. 602If less than eight bytes of pad are specified, no round trip times are 603given. 604.Sh DUPLICATE AND DAMAGED PACKETS 605The 606.Nm 607utility will report duplicate and damaged packets. 608Duplicate packets should never occur when pinging a unicast address, 609and seem to be caused by 610inappropriate link-level retransmissions. 611Duplicates may occur in many situations and are rarely 612(if ever) 613a good sign, although the presence of low levels of duplicates may not 614always be cause for alarm. 615Duplicates are expected when pinging a broadcast or multicast address, 616since they are not really duplicates but replies from different hosts 617to the same request. 618.Pp 619Damaged packets are obviously serious cause for alarm and often 620indicate broken hardware somewhere in the 621.Nm 622packet's path (in the network or in the hosts). 623.Sh TRYING DIFFERENT DATA PATTERNS 624The 625(inter)network 626layer should never treat packets differently depending on the data 627contained in the data portion. 628Unfortunately, data-dependent problems have been known to sneak into 629networks and remain undetected for long periods of time. 630In many cases the particular pattern that will have problems is something 631that does not have sufficient 632.Dq transitions , 633such as all ones or all zeros, or a pattern right at the edge, such as 634almost all zeros. 635It is not 636necessarily enough to specify a data pattern of all zeros (for example) 637on the command line because the pattern that is of interest is 638at the data link level, and the relationship between what you type and 639what the controllers transmit can be complicated. 640.Pp 641This means that if you have a data-dependent problem you will probably 642have to do a lot of testing to find it. 643If you are lucky, you may manage to find a file that either 644cannot 645be sent across your network or that takes much longer to transfer than 646other similar length files. 647You can then examine this file for repeated patterns that you can test 648using the 649.Fl p 650option of 651.Nm . 652.Sh IPv4 TTL DETAILS 653The 654TTL 655value of an IP packet represents the maximum number of IP routers 656that the packet can go through before being thrown away. 657In current practice you can expect each router in the Internet to decrement 658the 659TTL 660field by exactly one. 661.Pp 662The 663TCP/IP 664specification recommends setting the 665TTL 666field for 667IP 668packets to 64. 669.Pp 670The maximum possible value of this field is 255, and some 671.Ux 672systems set 673the 674TTL 675field of 676ICMP ECHO_REQUEST 677packets to 255. 678This is why you will find you can 679.Dq ping 680some hosts, but not reach them with 681.Xr telnet 1 682or 683.Xr ftp 1 . 684.Pp 685In normal operation 686.Nm 687prints the ttl value from the packet it receives. 688When a remote system receives a ping packet, it can do one of three things 689with the 690TTL 691field in its response: 692.Bl -bullet 693.It 694Not change it; this is what 695.Bx 696systems did before the 697.Bx 4.3 tahoe 698release. 699In this case the 700TTL 701value in the received packet will be 255 minus the 702number of routers in the round-trip path. 703.It 704Set it to 64; this is what current 705.Fx 706systems do. 707In this case the 708TTL 709value in the received packet will be 64 minus the 710number of routers in the path 711.Em from 712the remote system 713.Em to 714the 715.Nm Ns Em ing 716host. 717.It 718Set it to some other value. 719Some machines use the same value for 720ICMP 721packets that they use for 722TCP 723packets, for example either 30 or 60. 724Others may use completely wild values. 725.El 726.Sh EXIT STATUS 727The 728.Nm 729utility exits with one of the following values: 730.Bl -tag -width indent 731.It 0 732At least one response was heard from the specified 733.Ar host . 734.It 2 735The transmission was successful but no responses were received. 736.It any other value 737An error occurred. 738.El 739.Sh EXAMPLES 740The following will send ICMPv6 echo request to 741.Li dst.example.com . 742.Bd -literal -offset indent 743ping -6 -n dst.example.com 744.Ed 745.Pp 746The following will probe hostnames for all nodes on the network link attached to 747.Li wi0 748interface. 749The address 750.Li ff02::1 751is named the link-local all-node multicast address, and the packet would 752reach every node on the network link. 753.Bd -literal -offset indent 754ping -6 -y ff02::1%wi0 755.Ed 756.Pp 757The following will probe addresses assigned to the destination node, 758.Li dst.example.com . 759.Bd -literal -offset indent 760ping -6 -k agl dst.example.com 761.Ed 762.Sh SEE ALSO 763.Xr netstat 1 , 764.Xr icmp 4 , 765.Xr icmp6 4 , 766.Xr inet6 4 , 767.Xr ip6 4 , 768.Xr ifconfig 8 , 769.Xr routed 8 , 770.Xr traceroute 8 , 771.Xr traceroute6 8 772.Rs 773.%A A. Conta 774.%A S. Deering 775.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification" 776.%N RFC 2463 777.%D December 1998 778.Re 779.Rs 780.%A Matt Crawford 781.%T "IPv6 Node Information Queries" 782.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt 783.%D May 2002 784.%O work in progress material 785.Re 786.Sh HISTORY 787The 788.Nm 789utility appeared in 790.Bx 4.3 . 791The 792.Nm ping6 793utility with IPv6 support first appeared in the WIDE Hydrangea IPv6 794protocol stack kit. 795.Pp 796IPv6 and IPsec support based on the KAME Project 797.Pq Pa https://www.kame.net/ 798stack was initially integrated into 799.Fx 4.0 . 800.Pp 801The 802.Nm ping6 803utility was merged to 804.Nm 805in Google Summer of Code 2019. 806.Sh AUTHORS 807The original 808.Nm 809utility was written by 810.An Mike Muuss 811while at the US Army Ballistics 812Research Laboratory. 813.Sh BUGS 814Many Hosts and Gateways ignore the IPv4 815RECORD_ROUTE 816option. 817.Pp 818The maximum IP header length is too small for options like 819RECORD_ROUTE 820to be completely useful. 821.No There Ap s 822not much that can be done about this, however. 823.Pp 824Flood pinging is not recommended in general, and flood pinging the 825broadcast address should only be done under very controlled conditions. 826.Pp 827The 828.Fl v 829option is not worth much on busy hosts. 830