fix man page to use marcos instead of parens, quotes and braces
plus other minor fixes
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7c66c05d49
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50ceac8822
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=23304
139
sbin/ping/ping.8
139
sbin/ping/ping.8
@ -30,7 +30,7 @@
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ping.8 8.2 (Berkeley) 12/11/93
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.\" $Id: ping.8,v 1.9 1997/03/02 06:32:42 imp Exp $
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.\" $Id: ping.8,v 1.10 1997/03/02 20:01:07 imp Exp $
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.\"
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.Dd March 1, 1997
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.Dt PING 8
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@ -41,45 +41,48 @@
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.Tn ICMP ECHO_REQUEST
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packets to network hosts
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.Sh SYNOPSIS
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.Nm ping
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.Nm
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.Op Fl QRadfnqrv
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.Op Fl c Ar count
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.Op Fl i Ar wait
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.Op Fl l Ar preload
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.Op Fl p Ar pattern
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.Op Fl s Ar packetsize
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[
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.Ar host
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.Bo
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.Ar host |
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.Op Fl L
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.Op Fl I Ar interface
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.Op Fl T Ar ttl
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.Ar mcast-group
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]
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.Bc
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.Sh DESCRIPTION
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.Nm Ping
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uses the
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.Tn ICMP
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protocol's mandatory
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.No protocol Ap s mandatory
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.Tn ECHO_REQUEST
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datagram to elicit an
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.Tn ICMP ECHO_RESPONSE
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from a host or gateway.
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.Tn ECHO_REQUEST
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datagrams (``pings'') have an IP and
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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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header,
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followed by a
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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 ``pad'' bytes used to fill out the
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packet.
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The options are as follows:
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and then an arbitrary number of
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.Dq pad
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bytes used to fill out the packet. The options are as follows:
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.Bl -tag -width Ds
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.It Fl a
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Audible. Include a bell (ASCII 0x07) character in the output when any packet
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is received. This option is ignored if other format options are present.
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Audible. Include a bell
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.Pq ASCII 0x07
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character in the output when any packet is received. This option is ignored
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if other format options are present.
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.It Fl c Ar count
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Stop after sending (and receiving)
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Stop after sending
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.Pq and receiving
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.Ar count
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.Tn ECHO_RESPONSE
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packets.
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@ -93,7 +96,9 @@ Outputs packets as fast as they come back or one hundred times per second,
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whichever is more.
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For every
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.Tn ECHO_REQUEST
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sent a period ``.'' is printed, while for every
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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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received a backspace is printed.
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This provides a rapid display of how many packets are being dropped.
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@ -128,7 +133,9 @@ This flag only applies if the ping destination is a multicast address.
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Numeric output only.
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No attempt will be made to lookup symbolic names for host addresses.
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.It Fl p Ar pattern
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You may specify up to 16 ``pad'' bytes to fill out the packet you send.
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You may specify up to 16
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.Dq pad
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bytes to fill out the packet you send.
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This is useful for diagnosing data-dependent problems in a network.
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For example,
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.Dq Li \-p ff
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@ -136,7 +143,8 @@ will cause the sent packet to be filled with all
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ones.
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.It Fl Q
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Somewhat quiet output.
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Don't display ICMP error messages that are in response to our query messages.
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.No Don Ap t
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display ICMP error messages that are in response to our query messages.
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Originally, the
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.Fl v
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flag was required to display such errors, but
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@ -173,8 +181,11 @@ Bypass the normal routing tables and send directly to a host on an attached
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network.
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If the host is not on a directly-attached network, an error is returned.
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This option can be used to ping a local host through an interface
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that has no route through it (e.g., after the interface was dropped by
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.Xr routed 8 ) .
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that has no route through it
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.Po
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e.g., after the interface was dropped by
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.Xr routed 8
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.Pc .
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.It Fl s Ar packetsize
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Specifies the number of data bytes to be sent.
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The default is 56, which translates into 64
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@ -195,47 +206,46 @@ that are received are listed.
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.El
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.Pp
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When using
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.Nm ping
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.Nm
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for fault isolation, it should first be run on the local host, to verify
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that the local network interface is up and running.
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Then, hosts and gateways further and further away should be ``pinged''.
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Then, hosts and gateways further and further away should be
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.Dq pinged .
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Round-trip times and packet loss statistics are computed.
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If duplicate packets are received, they are not included in the packet
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loss calculation, although the round trip time of these packets is used
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in calculating the minimum/average/maximum round-trip time numbers.
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When the specified number of packets have been sent (and received) or
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if the program is terminated with a
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When the specified number of packets have been sent
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.Pq and received
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or if the program is terminated with a
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.Dv SIGINT ,
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a brief summary is displayed.
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.Pp
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This program is intended for use in network testing, measurement and
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management.
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Because of the load it can impose on the network, it is unwise to use
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.Nm ping
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.Nm
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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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packet contains an additional 8 bytes worth
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of
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packet contains an additional 8 bytes worth of
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.Tn 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 (the
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default is 56).
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is given, this indicated the size of this extra piece of data
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.Pq 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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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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header).
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.Pq the Tn ICMP header .
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.Pp
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If the data space is at least eight bytes large,
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.Nm ping
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.Nm
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uses the first eight bytes of this space to include a timestamp which
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it uses in the computation of round trip times.
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If less than eight bytes of pad are specified, no round trip times are
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@ -246,8 +256,9 @@ will report duplicate and damaged packets.
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Duplicate packets should never occur when pinging a unicast address,
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and seem to be caused by
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inappropriate link-level retransmissions.
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Duplicates may occur in many situations and are rarely (if ever) a
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good sign, although the presence of low levels of duplicates may not
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Duplicates may occur in many situations and are rarely
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.Pq if ever
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a good sign, although the presence of low levels of duplicates may not
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always be cause for alarm.
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Duplicates are expected when pinging a broadcast or multicast address,
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since they are not really duplicates but replies from different hosts
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@ -256,30 +267,40 @@ to the same request.
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Damaged packets are obviously serious cause for alarm and often
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indicate broken hardware somewhere in the
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.Nm ping
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packet's path (in the network or in the hosts).
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.No packet Ap s path
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.Pq in the network or in the hosts .
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.Sh TRYING DIFFERENT DATA PATTERNS
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The (inter)network layer should never treat packets differently depending
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on the data contained in the data portion.
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The
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.Po
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inter
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.Pc Ns network
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layer should never treat packets differently depending on the data
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contained in the data portion.
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Unfortunately, data-dependent problems have been known to sneak into
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networks and remain undetected for long periods of time.
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In many cases the particular pattern that will have problems is something
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that doesn't have sufficient ``transitions'', such as all ones or all
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zeros, or a pattern right at the edge, such as almost all zeros.
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It isn't necessarily enough to specify a data pattern of all zeros (for
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example) on the command line because the pattern that is of interest is
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.No that doesn Ap t have sufficient
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.Dq transitions ,
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such as all ones or all zeros, or a pattern right at the edge, such as
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almost all zeros.
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.No It isn Ap t
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necessarily enough to specify a data pattern of all zeros
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.Pq for example
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on the command line because the pattern that is of interest is
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at the data link level, and the relationship between what you type and
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what the controllers transmit can be complicated.
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.Pp
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This means that if you have a data-dependent problem you will probably
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have to do a lot of testing to find it.
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If you are lucky, you may manage to find a file that either can't be sent
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across your network or that takes much longer to transfer than other
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similar length files.
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If you are lucky, you may manage to find a file that either
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.No can Ap t
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be sent across your network or that takes much longer to transfer than
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other similar length files.
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You can then examine this file for repeated patterns that you can test
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using the
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.Fl p
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option of
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.Nm ping .
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.Nm Ns .
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.Sh TTL DETAILS
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The
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.Tn TTL
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@ -296,11 +317,8 @@ specification states that the
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.Tn TTL
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field for
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.Tn TCP
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packets should
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be set to 60, but many systems use smaller values (4.3
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.Tn BSD
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uses 30, 4.2 used
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15).
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packets should be set to 60, but many systems use smaller values
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.Pq Bx 4.3 \ uses 30, Bx 4.2 \ used 15 .
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.Pp
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The maximum possible value of this field is 255, and most Unix systems set
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the
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@ -308,8 +326,9 @@ the
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field of
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.Tn ICMP ECHO_REQUEST
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packets to 255.
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This is why you will find you can ``ping'' some hosts, but not reach them
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with
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This is why you will find you can
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.Dq ping
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some hosts, but not reach them with
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.Xr telnet 1
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or
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.Xr ftp 1 .
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@ -334,11 +353,11 @@ 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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number of routers in the path
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.Xr from
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.Em from
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the remote system
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.Em to
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the
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.Nm ping Ns Em ing
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.Nm Ns Em ing
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host.
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.It
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Set it to some other value.
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@ -351,7 +370,7 @@ Others may use completely wild values.
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.El
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.Sh RETURN VALUES
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The
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.Nm ping
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.Nm
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command returns an exit status of zero if at least one response was
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heard from the specified
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.Ar host ;
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@ -381,9 +400,9 @@ 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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to
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be completely useful.
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There's not much that can be done about this, however.
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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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.Pp
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Flood pinging is not recommended in general, and flood pinging the
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broadcast address should only be done under very controlled conditions.
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