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ping(8): man page cleanup
* Appease mandoc -T lint and igor
* Use example.com for documentation
* Update the IPv4 TTL section.
Update the IPv4 TTL section specifically for FreeBSD.
FreeBSD changed the default TTL to 64 in
5639e86bdd. NetBSD and OpenBSD still
use 255. Remove some references of extinct operating systems.
Reviewed by: gbe (manpages), asomers
MFC after: 2 weeks
Pull Request: https://github.com/freebsd/freebsd-src/pull/630
This commit is contained in:
Jose Luis Duran
Alan Somers
parent
5affc86b80
commit
8eb4df9487
144
sbin/ping/ping.8
144
sbin/ping/ping.8
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@ -28,15 +28,15 @@
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.\" @(#)ping.8 8.2 (Berkeley) 12/11/93
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.\" $FreeBSD$
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.\"
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.Dd November 26, 2020
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.Dd November 20, 2022
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.Dt PING 8
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.Os
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.Sh NAME
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.Nm ping
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.Nd send
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.Tn ICMP
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ICMP
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or
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.Tn ICMPv6 ECHO_REQUEST
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ICMPv6 ECHO_REQUEST
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packets to network hosts
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.Sh SYNOPSIS
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.Nm
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@ -101,19 +101,21 @@ packets to network hosts
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The
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.Nm
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utility invoked with an IPv4 target
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.Ns ( Ar IPv4-host No or Ar IPv4-mcast-group Ns )
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.Ar ( IPv4-host
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or
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.Ar IPv4-mcast-group )
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uses the
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.Tn ICMP
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ICMP
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.No protocol Ap s mandatory
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.Tn ECHO_REQUEST
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ECHO_REQUEST
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datagram to elicit an
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.Tn ICMP ECHO_RESPONSE
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ICMP ECHO_RESPONSE
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from a host or gateway.
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.Tn ECHO_REQUEST
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ECHO_REQUEST
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datagrams
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.Pq Dq pings
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have an IP and
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.Tn ICMP
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ICMP
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header, followed by a
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.Dq struct timeval
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and then an arbitrary number of
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@ -121,24 +123,26 @@ and then an arbitrary number of
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bytes used to fill out the packet.
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.Pp
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When invoked with an IPv6 target
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.Ns ( Ar IPv6-host Ns ) Ns ,
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.Ar ( IPv6-host ) ,
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it uses the
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.Tn ICMPv6
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ICMPv6
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protocol's mandatory
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.Tn ICMP6_ECHO_REQUEST
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ICMP6_ECHO_REQUEST
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datagram to elicit an
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.Tn ICMP6_ECHO_REPLY
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.Ns .
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.Tn ICMP6_ECHO_REQUEST
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ICMP6_ECHO_REPLY.
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ICMP6_ECHO_REQUEST
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datagrams have an IPv6 header and
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.Tn ICMPv6
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ICMPv6
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header formatted as documented in RFC 2463.
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.Pp
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When invoked with a hostname, the version to which the target is resolved first is used.
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In that case, the options and arguments used must be valid for the specific IP version, otherwise
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When invoked with a hostname, the version to which the target is resolved first
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is used.
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In that case, the options and arguments used must be valid for the specific IP
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version, otherwise
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.Nm
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exits with an error.
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If the target is resolved to both IPv4 and IPv6, the specific IP version can be requested by
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If the target is resolved to both IPv4 and IPv6, the specific IP version can be
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requested by
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.Fl 4
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or
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.Fl 6
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@ -150,11 +154,11 @@ as
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.Bl -tag -width indent
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.It Fl .\& Ns Ar chars
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By default, for every
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.Tn ECHO_REQUEST
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ECHO_REQUEST
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sent, a period
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.Dq .\&
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is printed, while for every
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.Tn ECHO_REPLY
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ECHO_REPLY
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received, a backspace is printed.
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This option takes an optional string argument listing characters
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that will be printed one by one in the provided order
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@ -167,7 +171,7 @@ ping -.0123456789 freebsd.org
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.It Fl A
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Audible.
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Output a bell
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.Tn ( ASCII
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(ASCII
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0x07)
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character when no packet is received before the next packet
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is transmitted.
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@ -177,7 +181,7 @@ if the maximum number of unreceived packets has increased.
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.It Fl a
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Audible.
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Include a bell
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.Tn ( ASCII
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(ASCII
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0x07)
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character in the output when any packet is received.
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.It Fl C Ar pcp
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@ -187,7 +191,7 @@ Add an 802.1p Ethernet Priority Code Point when sending a packet.
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Stop after sending
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(and receiving)
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.Ar count
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.Tn ECHO_RESPONSE
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ECHO_RESPONSE
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packets.
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If this option is not specified,
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.Nm
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@ -210,9 +214,9 @@ whichever is more.
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Implies
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.Fl .\&
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to print a period for every
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.Tn ECHO_REQUEST
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ECHO_REQUEST
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sent and a backspace for every
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.Tn ECHO_REPLY
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ECHO_REPLY
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received.
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This provides a rapid display of how many packets are being dropped.
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Only the super-user may use this option.
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@ -233,9 +237,9 @@ This flag applies only if the ping target is a multicast address.
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.Pp
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For an IPv6 target,
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.Ar iface
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is a name of an interface (e.g. `em0') from which the packets will be sent.
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This flag applies if the ping target is a multicast address, or link-local/site-local
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unicast address.
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is a name of an interface (e.g., `em0') from which the packets will be sent.
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This flag applies if the ping target is a multicast address, or
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link-local/site-local unicast address.
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.It Fl i Ar wait
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Wait
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.Ar wait
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@ -304,10 +308,10 @@ the sending node, and must be numeric.
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.It Fl s Ar packetsize
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Specify the number of data bytes to be sent.
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The default is 56, which translates into 64
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.Tn ICMP
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ICMP
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data bytes when combined
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with the 8 bytes of
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.Tn ICMP
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ICMP
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header data.
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.Pp
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For IPv4, only the super-user may specify values more than default.
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@ -321,9 +325,9 @@ Specify a timeout, in seconds, before ping exits regardless of how
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many packets have been received.
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.It Fl v
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Verbose output.
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.Tn ICMP
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ICMP
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packets other than
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.Tn ECHO_RESPONSE
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ECHO_RESPONSE
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that are received are listed.
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.It Fl W Ar waittime
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Time in milliseconds to wait for a reply for each packet sent.
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@ -336,17 +340,17 @@ considered as replied when calculating statistics.
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Use IPv4 regardless of how the target is resolved.
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.It Fl G Ar sweepmaxsize
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Specify the maximum size of
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.Tn ICMP
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ICMP
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payload when sending sweeping pings.
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This option is required for ping sweeps.
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.It Fl g Ar sweepminsize
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Specify the size of
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.Tn ICMP
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ICMP
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payload to start with when sending sweeping pings.
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The default value is 0.
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.It Fl h Ar sweepincrsize
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Specify the number of bytes to increment the size of
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.Tn ICMP
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ICMP
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payload after
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each sweep when sending sweeping pings.
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The default value is 1.
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@ -396,9 +400,9 @@ messages.
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.It Fl R
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Record route.
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Includes the
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.Tn RECORD_ROUTE
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RECORD_ROUTE
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option in the
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.Tn ECHO_REQUEST
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ECHO_REQUEST
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packet and displays
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the route buffer on returned packets.
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Note that the IP header is only large enough for nine such routes;
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@ -410,7 +414,7 @@ If more routes come back than should, such as due to an illegal spoofed
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packet, ping will print the route list and then truncate it at the correct
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spot.
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Many hosts ignore or discard the
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.Tn RECORD_ROUTE
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RECORD_ROUTE
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option.
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.It Fl r
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Bypass the normal routing tables and send directly to a host on an attached
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@ -575,21 +579,21 @@ during normal operations or from automated scripts.
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.Sh ICMP PACKET DETAILS
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An IP header without options is 20 bytes.
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An
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.Tn ICMP
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.Tn ECHO_REQUEST
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ICMP
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ECHO_REQUEST
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packet contains an additional 8 bytes worth of
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.Tn ICMP
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ICMP
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header followed by an arbitrary amount of data.
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When a
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.Ar packetsize
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is given, this indicated the size of this extra piece of data
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(the default is 56).
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Thus the amount of data received inside of an IP packet of type
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.Tn ICMP
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.Tn ECHO_REPLY
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ICMP
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ECHO_REPLY
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will always be 8 bytes more than the requested data space
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(the
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.Tn ICMP
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ICMP
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header).
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.Pp
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If the data space is at least eight bytes large,
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@ -648,33 +652,29 @@ option of
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.Nm .
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.Sh IPv4 TTL DETAILS
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The
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.Tn TTL
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TTL
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value of an IP packet represents the maximum number of IP routers
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that the packet can go through before being thrown away.
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In current practice you can expect each router in the Internet to decrement
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the
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.Tn TTL
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TTL
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field by exactly one.
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.Pp
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The
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.Tn TCP/IP
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TCP/IP
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specification recommends setting the
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.Tn TTL
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TTL
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field for
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.Tn IP
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packets to 64, but many systems use smaller values
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.No ( Bx 4.3
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uses 30,
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.Bx 4.2
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used 15).
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IP
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packets to 64.
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.Pp
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The maximum possible value of this field is 255, and most
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The maximum possible value of this field is 255, and some
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.Ux
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systems set
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the
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.Tn TTL
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TTL
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field of
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.Tn ICMP ECHO_REQUEST
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ICMP ECHO_REQUEST
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packets to 255.
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This is why you will find you can
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.Dq ping
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@ -688,7 +688,7 @@ In normal operation
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prints the ttl value from the packet it receives.
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When a remote system receives a ping packet, it can do one of three things
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with the
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.Tn TTL
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TTL
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field in its response:
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.Bl -bullet
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.It
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@ -698,16 +698,16 @@ systems did before the
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.Bx 4.3 tahoe
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release.
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In this case the
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.Tn TTL
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TTL
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value in the received packet will be 255 minus the
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number of routers in the round-trip path.
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.It
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Set it to 255; this is what current
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.Bx
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Set it to 64; this is what current
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.Fx
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systems do.
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In this case the
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.Tn TTL
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value in the received packet will be 255 minus the
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TTL
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value in the received packet will be 64 minus the
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number of routers in the path
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.Em from
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the remote system
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@ -718,9 +718,9 @@ host.
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.It
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Set it to some other value.
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Some machines use the same value for
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.Tn ICMP
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ICMP
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packets that they use for
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.Tn TCP
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TCP
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packets, for example either 30 or 60.
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Others may use completely wild values.
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.El
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@ -739,9 +739,9 @@ An error occurred.
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.El
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.Sh EXAMPLES
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The following will send ICMPv6 echo request to
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.Li dst.foo.com .
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.Li dst.example.com .
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.Bd -literal -offset indent
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ping -6 -n dst.foo.com
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ping -6 -n dst.example.com
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.Ed
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.Pp
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The following will probe hostnames for all nodes on the network link attached to
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@ -756,9 +756,9 @@ ping -6 -y ff02::1%wi0
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.Ed
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.Pp
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The following will probe addresses assigned to the destination node,
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.Li dst.foo.com .
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.Li dst.example.com .
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.Bd -literal -offset indent
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ping -6 -k agl dst.foo.com
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ping -6 -k agl dst.example.com
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.Ed
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.Sh SEE ALSO
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.Xr netstat 1 ,
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@ -813,11 +813,11 @@ while at the US Army Ballistics
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Research Laboratory.
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.Sh BUGS
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Many Hosts and Gateways ignore the IPv4
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.Tn RECORD_ROUTE
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RECORD_ROUTE
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option.
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.Pp
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The maximum IP header length is too small for options like
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.Tn RECORD_ROUTE
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RECORD_ROUTE
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to be completely useful.
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.No There Ap s
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not much that can be done about this, however.
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