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.Dd October 15, 2024 29.Dt PING 8 30.Os 31.Sh NAME 32.Nm ping 33.Nd send 34ICMP 35or 36ICMPv6 ECHO_REQUEST 37packets to network hosts 38.Sh SYNOPSIS 39.Nm 40.Op Fl 4AaDdfHnoQqRrv 41.Op Fl .\& Ns Ar chars 42.Op Fl C Ar pcp 43.Op Fl c Ar count 44.Op Fl G Ar sweepmaxsize 45.Op Fl g Ar sweepminsize 46.Op Fl h Ar sweepincrsize 47.Op Fl i Ar wait 48.Op Fl l Ar preload 49.Op Fl M Cm mask | time 50.Op Fl m Ar ttl 51.Op Fl P Ar policy 52.Op Fl p Ar pattern 53.Op Fl S Ar src_addr 54.Op Fl s Ar packetsize 55.Op Fl t Ar timeout 56.Op Fl W Ar waittime 57.Op Fl z Ar tos 58.Ar IPv4-host 59.Nm 60.Op Fl 4AaDdfHLnoQqRrv 61.Op Fl .\& Ns Ar chars 62.Op Fl C Ar pcp 63.Op Fl c Ar count 64.Op Fl I Ar iface 65.Op Fl i Ar wait 66.Op Fl l Ar preload 67.Op Fl M Cm mask | time 68.Op Fl m Ar ttl 69.Op Fl P Ar policy 70.Op Fl p Ar pattern 71.Op Fl S Ar src_addr 72.Op Fl s Ar packetsize 73.Op Fl T Ar ttl 74.Op Fl t Ar timeout 75.Op Fl W Ar waittime 76.Op Fl z Ar tos 77.Ar IPv4-mcast-group 78.Nm 79.Op Fl 6AaDdEfHNnOoquvYyZ 80.Op Fl .\& Ns Ar chars 81.Op Fl b Ar bufsiz 82.Op Fl C Ar pcp 83.Op Fl c Ar count 84.Op Fl e Ar gateway 85.Op Fl I Ar interface 86.Op Fl i Ar wait 87.Op Fl k Ar addrtype 88.Op Fl l Ar preload 89.Op Fl m Ar hoplimit 90.Op Fl P Ar policy 91.Op Fl p Ar pattern 92.Op Fl S Ar sourceaddr 93.Op Fl s Ar packetsize 94.Op Fl t Ar timeout 95.Op Fl W Ar waittime 96.Op Ar IPv6-hops ... 97.Ar IPv6-host 98.Sh DESCRIPTION 99The 100.Nm 101utility invoked with an IPv4 target 102.Ar ( IPv4-host 103or 104.Ar IPv4-mcast-group ) 105uses the 106ICMP 107.No protocol Ap s mandatory 108ECHO_REQUEST 109datagram to elicit an 110ICMP ECHO_RESPONSE 111from a host or gateway. 112ECHO_REQUEST 113datagrams 114.Pq Dq pings 115have an IP and 116ICMP 117header, followed by a 118.Dq struct timeval 119and then an arbitrary number of 120.Dq pad 121bytes used to fill out the packet. 122.Pp 123When invoked with an IPv6 target 124.Ar ( IPv6-host ) , 125it uses the 126ICMPv6 127protocol's mandatory 128ICMP6_ECHO_REQUEST 129datagram to elicit an 130ICMP6_ECHO_REPLY. 131ICMP6_ECHO_REQUEST 132datagrams have an IPv6 header and 133ICMPv6 134header formatted as documented in RFC 2463. 135.Pp 136When invoked with a hostname, the version to which the target is resolved first 137is used. 138In that case, the options and arguments used must be valid for the specific IP 139version, otherwise 140.Nm 141exits with an error. 142If the target is resolved to both IPv4 and IPv6, the specific IP version can be 143requested by 144.Fl 4 145or 146.Fl 6 147options, respectively. 148For backwards-compatibility, ICMPv6 can also be selected by invoking the binary 149as 150.Nm ping6 . 151.Ss Options common to both IPv4 and IPv6 targets 152.Bl -tag -width indent 153.It Fl .\& Ns Ar chars 154By default, for every 155ECHO_REQUEST 156sent, a period 157.Dq .\& 158is printed, while for every 159ECHO_REPLY 160received, a backspace is printed. 161This option takes an optional string argument listing characters 162that will be printed one by one in the provided order 163instead of the default period. 164.Pp 165Example usage: 166.Bd -literal -offset indent 167ping -.0123456789 freebsd.org 168.Ed 169.It Fl A 170Audible. 171Output a bell 172(ASCII 1730x07) 174character when no packet is received before the next packet 175is transmitted. 176To cater for round-trip times that are longer than the interval 177between transmissions, further missing packets cause a bell only 178if the maximum number of unreceived packets has increased. 179.It Fl a 180Audible. 181Include a bell 182(ASCII 1830x07) 184character in the output when any packet is received. 185.It Fl C Ar pcp 186Add an 802.1p Ethernet Priority Code Point when sending a packet. 1870..7 uses that specific PCP, -1 uses the interface default PCP (or none). 188.It Fl c Ar count 189Stop after sending 190(and receiving) 191.Ar count 192ECHO_RESPONSE 193packets. 194If this option is not specified, 195.Nm 196will operate until interrupted. 197.Pp 198For an IPv4 target, if this option is specified in conjunction with ping sweeps, 199each sweep will consist of 200.Ar count 201packets. 202.It Fl D 203Disable fragmentation. 204.It Fl d 205Set the 206.Dv SO_DEBUG 207option on the socket being used. 208.It Fl f 209Flood ping. 210Outputs packets as fast as they come back or one hundred times per second, 211whichever is more. 212Implies 213.Fl .\& 214to print a period for every 215ECHO_REQUEST 216sent and a backspace for every 217ECHO_REPLY 218received. 219This provides a rapid display of how many packets are being dropped. 220Only the super-user may use this option. 221.Bf -emphasis 222This can be very hard on a network and should be used with caution. 223.Ef 224.It Fl H 225Hostname output. 226Try to do a reverse DNS lookup when displaying addresses. 227This is the opposite of the 228.Fl n 229option. 230.It Fl I Ar iface 231For an IPv4 target, 232.Ar iface 233is an IP address indentifying an interface from which the packets will be sent. 234This flag applies only if the ping target is a multicast address. 235.Pp 236For an IPv6 target, 237.Ar iface 238is a name of an interface (e.g., `em0') from which the packets will be sent. 239This flag applies if the ping target is a multicast address, or 240link-local/site-local unicast address. 241.It Fl i Ar wait 242Wait 243.Ar wait 244seconds 245.Em between sending each packet . 246The default is to wait for one second between each packet. 247The wait time may be fractional, but only the super-user may specify 248values less than 1 second. 249This option is incompatible with the 250.Fl f 251option. 252.It Fl l Ar preload 253If 254.Ar preload 255is specified, 256.Nm 257sends that many packets as fast as possible before falling into its normal 258mode of behavior. 259Only the super-user may use this option. 260.It Fl m Ar ttl 261For an IPv4 target, set the IP Time To Live for outgoing packets. 262If not specified, the kernel uses the value of the 263.Va net.inet.ip.ttl 264MIB variable. 265.Pp 266For an IPv6 target, set the IPv6 hoplimit. 267.It Fl n 268Numeric output only. 269No attempt will be made to lookup symbolic names for host addresses. 270This is the opposite of 271.Fl H , 272and it is the default behavior. 273.It Fl o 274Exit successfully after receiving one reply packet. 275.It Fl P Ar policy 276.Ar policy 277specifies IPsec policy for the ping session. 278For details please refer to 279.Xr ipsec 4 280and 281.Xr ipsec_set_policy 3 . 282.It Fl p Ar pattern 283You may specify up to 16 284.Dq pad 285bytes to fill out the packet you send. 286This is useful for diagnosing data-dependent problems in a network. 287For example, 288.Dq Li \-p ff 289will cause the sent packet to be filled with all 290ones. 291.It Fl q 292Quiet output. 293Nothing is displayed except the summary lines at startup time and 294when finished. 295.It Fl S Ar src_addr 296Use the following IP address as the source address in outgoing packets. 297On hosts with more than one IP address, this option can be used to 298force the source address to be something other than the IP address 299of the interface the probe packet is sent on. 300.Pp 301For IPv4, if the IP address is not one of this machine's interface 302addresses, an error is returned and nothing is sent. 303.Pp 304For IPv6, the source address must be one of the unicast addresses of 305the sending node, and must be numeric. 306.It Fl s Ar packetsize 307Specify the number of data bytes to be sent. 308The default is 56, which translates into 64 309ICMP 310data bytes when combined 311with the 8 bytes of 312ICMP 313header data. 314.Pp 315This option cannot be used with ping sweeps. 316.Pp 317For IPv6, you may need to specify 318.Fl b 319as well to extend socket buffer size. 320.It Fl t Ar timeout 321Specify a timeout, in seconds, before ping exits regardless of how 322many packets have been received. 323.It Fl v 324Verbose output. 325ICMP 326packets other than 327ECHO_RESPONSE 328that are received are listed. 329.It Fl W Ar waittime 330Time in milliseconds to wait for a reply for each packet sent. 331If a reply arrives later, the packet is not printed as replied, but 332considered as replied when calculating statistics. 333.El 334.Ss Options only for IPv4 targets 335.Bl -tag -width indent 336.It Fl 4 337Use IPv4 regardless of how the target is resolved. 338.It Fl G Ar sweepmaxsize 339Specify the maximum size of 340ICMP 341payload when sending sweeping pings. 342This option is required for ping sweeps. 343.It Fl g Ar sweepminsize 344Specify the size of 345ICMP 346payload to start with when sending sweeping pings. 347The default value is 0. 348.It Fl h Ar sweepincrsize 349Specify the number of bytes to increment the size of 350ICMP 351payload after 352each sweep when sending sweeping pings. 353The default value is 1. 354.It Fl L 355Suppress loopback of multicast packets. 356This flag only applies if the ping destination is a multicast address. 357.It Fl M Cm mask | time 358Use 359.Dv ICMP_MASKREQ 360or 361.Dv ICMP_TSTAMP 362instead of 363.Dv ICMP_ECHO . 364For 365.Cm mask , 366print the netmask of the remote machine. 367Set the 368.Va net.inet.icmp.maskrepl 369MIB variable to enable 370.Dv ICMP_MASKREPLY 371and 372.Va net.inet.icmp.maskfake 373if you want to override the netmask in the response. 374For 375.Cm time , 376print the origination, reception and transmission timestamps. 377Set the 378.Va net.inet.icmp.tstamprepl 379MIB variable to enable or disable 380.Dv ICMP_TSTAMPREPLY . 381.It Fl Q 382Somewhat quiet output. 383.No Don Ap t 384display ICMP error messages that are in response to our query messages. 385Originally, the 386.Fl v 387flag was required to display such errors, but 388.Fl v 389displays all ICMP error messages. 390On a busy machine, this output can be overbearing. 391Without the 392.Fl Q 393flag, 394.Nm 395prints out any ICMP error messages caused by its own ECHO_REQUEST 396messages. 397.It Fl R 398Record route. 399Includes the 400RECORD_ROUTE 401option in the 402ECHO_REQUEST 403packet and displays 404the route buffer on returned packets. 405Note that the IP header is only large enough for nine such routes; 406the 407.Xr traceroute 8 408command is usually better at determining the route packets take to a 409particular destination. 410If more routes come back than should, such as due to an illegal spoofed 411packet, ping will print the route list and then truncate it at the correct 412spot. 413Many hosts ignore or discard the 414RECORD_ROUTE 415option. 416.It Fl r 417Bypass the normal routing tables and send directly to a host on an attached 418network. 419If the host is not on a directly-attached network, an error is returned. 420This option can be used to ping a local host through an interface 421that has no route through it 422(e.g., after the interface was dropped by 423.Xr routed 8 ) . 424.It Fl T Ar ttl 425Set the IP Time To Live for multicasted packets. 426This flag only applies if the ping destination is a multicast address. 427.It Fl z Ar tos 428Use the specified type of service. 429.It Ar IPv4-host 430hostname or IPv4 address of the final destination node. 431.It Ar IPv4-mcast-group 432IPv4 multicast address of the final destination nodes. 433.El 434.Ss Options only for IPv6 targets 435.Bl -tag -width indent 436.It Fl 6 437Use IPv6 regardless of how the target is resolved. 438.It Fl b Ar bufsiz 439Set socket buffer size. 440.It Fl e Ar gateway 441Specifies to use 442.Ar gateway 443as the next hop to the destination. 444The gateway must be a neighbor of the sending node. 445.It Fl k Ar addrtype 446Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. 447.Ar addrtype 448must be a string constructed of the following characters. 449.Bl -tag -width Ds -compact 450.It Ic a 451requests unicast addresses from all of the responder's interfaces. 452If the character is omitted, 453only those addresses which belong to the interface which has the 454responder's address are requests. 455.It Ic c 456requests responder's IPv4-compatible and IPv4-mapped addresses. 457.It Ic g 458requests responder's global-scope addresses. 459.It Ic s 460requests responder's site-local addresses. 461.It Ic l 462requests responder's link-local addresses. 463.It Ic A 464requests responder's anycast addresses. 465Without this character, the responder will return unicast addresses only. 466With this character, the responder will return anycast addresses only. 467Note that the specification does not specify how to get responder's 468anycast addresses. 469This is an experimental option. 470.El 471.It Fl N 472Probe node information multicast group address 473.Pq Li ff02::2:ffxx:xxxx . 474.Ar host 475must be string hostname of the target 476(must not be a numeric IPv6 address). 477Node information multicast group will be computed based on given 478.Ar host , 479and will be used as the final destination. 480Since node information multicast group is a link-local multicast group, 481outgoing interface needs to be specified by 482.Fl I 483option. 484.Pp 485When specified twice, the address 486.Pq Li ff02::2:xxxx:xxxx 487is used instead. 488The former is in RFC 4620, the latter is in an old Internet Draft 489draft-ietf-ipngwg-icmp-name-lookup. 490Note that KAME-derived implementations including 491.Fx 492use the latter. 493.It Fl O 494Generate ICMPv6 Node Information supported query types query, 495rather than echo-request. 496.Fl s 497has no effect if 498.Fl O 499is specified. 500.It Fl u 501By default, 502.Nm 503asks the kernel to fragment packets to fit into the minimum IPv6 MTU. 504The 505.Fl u 506option 507will suppress the behavior in the following two levels: 508when the option is specified once, the behavior will be disabled for 509unicast packets. 510When the option is more than once, it will be disabled for both 511unicast and multicast packets. 512.It Fl Y 513Same as 514.Fl y , 515but with old packet format based on 03 draft. 516This option is present for backward compatibility. 517.Fl s 518has no effect if 519.Fl y 520is specified. 521.It Fl y 522Generate ICMPv6 Node Information DNS Name query, rather than echo-request. 523.Fl s 524has no effect if 525.Fl y 526is specified. 527.It Ar IPv6-hops 528IPv6 addresses for intermediate nodes, 529which will be put into type 0 routing header. 530.It Ar IPv6-host 531IPv6 address of the final destination node. 532.El 533.Ss Experimental options only for IPv6 target 534.Bl -tag -width indent 535.It Fl E 536Enables transport-mode IPsec encapsulated security payload. 537.It Fl Z 538Enables transport-mode IPsec authentication header. 539.El 540.Pp 541When using 542.Nm 543for fault isolation, it should first be run on the local host, to verify 544that the local network interface is up and running. 545Then, hosts and gateways further and further away should be 546.Dq pinged . 547Round-trip times and packet loss statistics are computed. 548If duplicate packets are received, they are not included in the packet 549loss calculation, although the round trip time of these packets is used 550in calculating the round-trip time statistics. 551When the specified number of packets have been sent 552(and received) 553or if the program is terminated with a 554.Dv SIGINT , 555a brief summary is displayed, showing the number of packets sent and 556received, and the minimum, mean, maximum, and standard deviation of 557the round-trip times. 558.Pp 559If 560.Nm 561receives a 562.Dv SIGINFO 563(see the 564.Cm status 565argument for 566.Xr stty 1 ) 567signal, the current number of packets sent and received, and the 568minimum, mean, maximum, and standard deviation of the round-trip times 569will be written to the standard output. 570.Pp 571This program is intended for use in network testing, measurement and 572management. 573Because of the load it can impose on the network, it is unwise to use 574.Nm 575during normal operations or from automated scripts. 576.Sh ICMP PACKET DETAILS 577An IP header without options is 20 bytes. 578An 579ICMP 580ECHO_REQUEST 581packet contains an additional 8 bytes worth of 582ICMP 583header followed by an arbitrary amount of data. 584When a 585.Ar packetsize 586is given, this indicated the size of this extra piece of data 587(the default is 56). 588Thus the amount of data received inside of an IP packet of type 589ICMP 590ECHO_REPLY 591will always be 8 bytes more than the requested data space 592(the 593ICMP 594header). 595.Pp 596If the data space is at least eight bytes large, 597.Nm 598uses the first eight bytes of this space to include a timestamp which 599it uses in the computation of round trip times. 600If less than eight bytes of pad are specified, no round trip times are 601given. 602.Sh DUPLICATE AND DAMAGED PACKETS 603The 604.Nm 605utility will report duplicate and damaged packets. 606Duplicate packets should never occur when pinging a unicast address, 607and seem to be caused by 608inappropriate link-level retransmissions. 609Duplicates may occur in many situations and are rarely 610(if ever) 611a good sign, although the presence of low levels of duplicates may not 612always be cause for alarm. 613Duplicates are expected when pinging a broadcast or multicast address, 614since they are not really duplicates but replies from different hosts 615to the same request. 616.Pp 617Damaged packets are obviously serious cause for alarm and often 618indicate broken hardware somewhere in the 619.Nm 620packet's path (in the network or in the hosts). 621.Sh TRYING DIFFERENT DATA PATTERNS 622The 623(inter)network 624layer should never treat packets differently depending on the data 625contained in the data portion. 626Unfortunately, data-dependent problems have been known to sneak into 627networks and remain undetected for long periods of time. 628In many cases the particular pattern that will have problems is something 629that does not have sufficient 630.Dq transitions , 631such as all ones or all zeros, or a pattern right at the edge, such as 632almost all zeros. 633It is not 634necessarily enough to specify a data pattern of all zeros (for example) 635on the command line because the pattern that is of interest is 636at the data link level, and the relationship between what you type and 637what the controllers transmit can be complicated. 638.Pp 639This means that if you have a data-dependent problem you will probably 640have to do a lot of testing to find it. 641If you are lucky, you may manage to find a file that either 642cannot 643be sent across your network or that takes much longer to transfer than 644other similar length files. 645You can then examine this file for repeated patterns that you can test 646using the 647.Fl p 648option of 649.Nm . 650.Sh IPv4 TTL DETAILS 651The 652TTL 653value of an IP packet represents the maximum number of IP routers 654that the packet can go through before being thrown away. 655In current practice you can expect each router in the Internet to decrement 656the 657TTL 658field by exactly one. 659.Pp 660The 661TCP/IP 662specification recommends setting the 663TTL 664field for 665IP 666packets to 64. 667.Pp 668The maximum possible value of this field is 255, and some 669.Ux 670systems set 671the 672TTL 673field of 674ICMP ECHO_REQUEST 675packets to 255. 676This is why you will find you can 677.Dq ping 678some hosts, but not reach them with 679.Xr telnet 1 680or 681.Xr ftp 1 . 682.Pp 683In normal operation 684.Nm 685prints the ttl value from the packet it receives. 686When a remote system receives a ping packet, it can do one of three things 687with the 688TTL 689field in its response: 690.Bl -bullet 691.It 692Not change it; this is what 693.Bx 694systems did before the 695.Bx 4.3 tahoe 696release. 697In this case the 698TTL 699value in the received packet will be 255 minus the 700number of routers in the round-trip path. 701.It 702Set it to 64; this is what current 703.Fx 704systems do. 705In this case the 706TTL 707value in the received packet will be 64 minus the 708number of routers in the path 709.Em from 710the remote system 711.Em to 712the 713.Nm Ns Em ing 714host. 715.It 716Set it to some other value. 717Some machines use the same value for 718ICMP 719packets that they use for 720TCP 721packets, for example either 30 or 60. 722Others may use completely wild values. 723.El 724.Sh EXIT STATUS 725The 726.Nm 727utility exits with one of the following values: 728.Bl -tag -width indent 729.It 0 730At least one response was heard from the specified 731.Ar host . 732.It 2 733The transmission was successful but no responses were received. 734.It any other value 735An error occurred. 736.El 737.Sh EXAMPLES 738The following will send ICMPv6 echo request to 739.Li dst.example.com . 740.Bd -literal -offset indent 741ping -6 -n dst.example.com 742.Ed 743.Pp 744The following will probe hostnames for all nodes on the network link attached to 745.Li wi0 746interface. 747The address 748.Li ff02::1 749is named the link-local all-node multicast address, and the packet would 750reach every node on the network link. 751.Bd -literal -offset indent 752ping -6 -y ff02::1%wi0 753.Ed 754.Pp 755The following will probe addresses assigned to the destination node, 756.Li dst.example.com . 757.Bd -literal -offset indent 758ping -6 -k agl dst.example.com 759.Ed 760.Sh SEE ALSO 761.Xr netstat 1 , 762.Xr icmp 4 , 763.Xr icmp6 4 , 764.Xr inet6 4 , 765.Xr ip6 4 , 766.Xr ifconfig 8 , 767.Xr routed 8 , 768.Xr traceroute 8 , 769.Xr traceroute6 8 770.Rs 771.%A A. Conta 772.%A S. Deering 773.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification" 774.%N RFC 2463 775.%D December 1998 776.Re 777.Rs 778.%A Matt Crawford 779.%T "IPv6 Node Information Queries" 780.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt 781.%D May 2002 782.%O work in progress material 783.Re 784.Sh HISTORY 785The 786.Nm 787utility appeared in 788.Bx 4.3 . 789The 790.Nm ping6 791utility with IPv6 support first appeared in the WIDE Hydrangea IPv6 792protocol stack kit. 793.Pp 794IPv6 and IPsec support based on the KAME Project 795.Pq Pa https://www.kame.net/ 796stack was initially integrated into 797.Fx 4.0 . 798.Pp 799The 800.Nm ping6 801utility was merged to 802.Nm 803in Google Summer of Code 2019. 804.Sh AUTHORS 805The original 806.Nm 807utility was written by 808.An Mike Muuss 809while at the US Army Ballistics 810Research Laboratory. 811.Sh BUGS 812Many Hosts and Gateways ignore the IPv4 813RECORD_ROUTE 814option. 815.Pp 816The maximum IP header length is too small for options like 817RECORD_ROUTE 818to be completely useful. 819.No There Ap s 820not much that can be done about this, however. 821.Pp 822Flood pinging is not recommended in general, and flood pinging the 823broadcast address should only be done under very controlled conditions. 824.Pp 825The 826.Fl v 827option is not worth much on busy hosts. 828