NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ICMP PACKET DETAILS | DUPLICATE AND DAMAGED PACKETS | TRYING DIFFERENT DATA PATTERNS | TTL DETAILS | BUGS | SEE ALSO | HISTORY | SECURITY | AVAILABILITY | COLOPHON

PING(8)                            iputils                           PING(8)

NAME         top

       ping - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS         top

       ping [-aAbBdDfhLnOqrRUvV46] [-c count] [-F flowlabel] [-i interval]
            [-I interface] [-l preload] [-m mark] [-M pmtudisc_option]
            [-N nodeinfo_option] [-w deadline] [-W timeout] [-p pattern]
            [-Q tos] [-s packetsize] [-S sndbuf] [-t ttl]
            [-T timestamp option] [hop...] destination

DESCRIPTION         top

       ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to
       elicit an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST
       datagrams (“pings”) have an IP and ICMP header, followed by a struct
       timeval and then an arbitrary number of “pad” bytes used to fill out
       the packet.

       ping works with both IPv4 and IPv6. Using only one of them explicitly
       can be enforced by specifying -4 or -6.

       ping can also send IPv6 Node Information Queries (RFC4620).
       Intermediate hops may not be allowed, because IPv6 source routing was
       deprecated (RFC5095).

OPTIONS         top

       -4
           Use IPv4 only.

       -6
           Use IPv6 only.

       -a
           Audible ping.

       -A
           Adaptive ping. Interpacket interval adapts to round-trip time, so
           that effectively not more than one (or more, if preload is set)
           unanswered probe is present in the network. Minimal interval is
           200msec for not super-user. On networks with low rtt this mode is
           essentially equivalent to flood mode.

       -b
           Allow pinging a broadcast address.

       -B
           Do not allow ping to change source address of probes. The address
           is bound to one selected when ping starts.

       -c count
           Stop after sending count ECHO_REQUEST packets. With deadline
           option, ping waits for count ECHO_REPLY packets, until the
           timeout expires.

       -d
           Set the SO_DEBUG option on the socket being used. Essentially,
           this socket option is not used by Linux kernel.

       -D
           Print timestamp (unix time + microseconds as in gettimeofday)
           before each line.

       -f
           Flood ping. For every ECHO_REQUEST sent a period “.” is printed,
           while for ever ECHO_REPLY received a backspace is printed. This
           provides a rapid display of how many packets are being dropped.
           If interval is not given, it sets interval to zero and outputs
           packets as fast as they come back or one hundred times per
           second, whichever is more. Only the super-user may use this
           option with zero interval.

       -F flow label
           IPv6 only. Allocate and set 20 bit flow label (in hex) on echo
           request packets. If value is zero, kernel allocates random flow
           label.

       -h
           Show help.

       -i interval
           Wait interval seconds between sending each packet. The default is
           to wait for one second between each packet normally, or not to
           wait in flood mode. Only super-user may set interval to values
           less than 0.2 seconds.

       -I interface
           interface is either an address, or an interface name. If
           interface is an address, it sets source address to specified
           interface address. If interface in an interface name, it sets
           source interface to specified interface. For IPv6, when doing
           ping to a link-local scope address, link specification (by the
           '%'-notation in destination, or by this option) is required.

       -l preload
           If preload is specified, ping sends that many packets not waiting
           for reply. Only the super-user may select preload more than 3.

       -L
           Suppress loopback of multicast packets. This flag only applies if
           the ping destination is a multicast address.

       -m mark
           use mark to tag the packets going out. This is useful for variety
           of reasons within the kernel such as using policy routing to
           select specific outbound processing.

       -M pmtudisc_opt
           Select Path MTU Discovery strategy.  pmtudisc_option may be
           either do (prohibit fragmentation, even local one), want (do PMTU
           discovery, fragment locally when packet size is large), or dont
           (do not set DF flag).

       -N nodeinfo_option
           IPv6 only. Send ICMPv6 Node Information Queries (RFC4620),
           instead of Echo Request. CAP_NET_RAW capability is required.

           help
               Show help for NI support.

           name
               Queries for Node Names.

           ipv6
               Queries for IPv6 Addresses. There are several IPv6 specific
               flags.

               ipv6-global
                   Request IPv6 global-scope addresses.

               ipv6-sitelocal
                   Request IPv6 site-local addresses.

               ipv6-linklocal
                   Request IPv6 link-local addresses.

               ipv6-all
                   Request IPv6 addresses on other interfaces.

           ipv4
               Queries for IPv4 Addresses. There is one IPv4 specific flag.

               ipv4-all
                   Request IPv4 addresses on other interfaces.

           subject-ipv6=ipv6addr
               IPv6 subject address.

           subject-ipv4=ipv4addr
               IPv4 subject address.

           subject-name=nodename
               Subject name. If it contains more than one dot,
               fully-qualified domain name is assumed.

           subject-fqdn=nodename
               Subject name. Fully-qualified domain name is always assumed.

       -n
           Numeric output only. No attempt will be made to lookup symbolic
           names for host addresses.

       -O
           Report outstanding ICMP ECHO reply before sending next packet.
           This is useful together with the timestamp -D to log output to a
           diagnostic file and search for missing answers.

       -p pattern
           You may specify up to 16 “pad” bytes to fill out the packet you
           send. This is useful for diagnosing data-dependent problems in a
           network. For example, -p ff will cause the sent packet to be
           filled with all ones.

       -q
           Quiet output. Nothing is displayed except the summary lines at
           startup time and when finished.

       -Q tos
           Set Quality of Service -related bits in ICMP datagrams.  tos can
           be decimal (ping only) or hex number.

           In RFC2474, these fields are interpreted as 8-bit Differentiated
           Services (DS), consisting of: bits 0-1 (2 lowest bits) of
           separate data, and bits 2-7 (highest 6 bits) of Differentiated
           Services Codepoint (DSCP). In RFC2481 and RFC3168, bits 0-1 are
           used for ECN.

           Historically (RFC1349, obsoleted by RFC2474), these were
           interpreted as: bit 0 (lowest bit) for reserved (currently being
           redefined as congestion control), 1-4 for Type of Service and
           bits 5-7 (highest bits) for Precedence.

       -r
           Bypass the normal routing tables and send directly to a host on
           an attached interface. If the host is not on a directly-attached
           network, an error is returned. This option can be used to ping a
           local host through an interface that has no route through it
           provided the option -I is also used.

       -R
           ping only. Record route. Includes the RECORD_ROUTE option in the
           ECHO_REQUEST packet and displays the route buffer on returned
           packets. Note that the IP header is only large enough for nine
           such routes. Many hosts ignore or discard this option.

       -s packetsize
           Specifies the number of data bytes to be sent. The default is 56,
           which translates into 64 ICMP data bytes when combined with the 8
           bytes of ICMP header data.

       -S sndbuf
           Set socket sndbuf. If not specified, it is selected to buffer not
           more than one packet.

       -t ttl
           ping only. Set the IP Time to Live.

       -T timestamp option
           Set special IP timestamp options.  timestamp option may be either
           tsonly (only timestamps), tsandaddr (timestamps and addresses) or
           tsprespec host1 [host2 [host3 [host4]]] (timestamp prespecified
           hops).

       -U
           Print full user-to-user latency (the old behaviour). Normally
           ping prints network round trip time, which can be different f.e.
           due to DNS failures.

       -v
           Verbose output.

       -V
           Show version and exit.

       -w deadline
           Specify a timeout, in seconds, before ping exits regardless of
           how many packets have been sent or received. In this case ping
           does not stop after count packet are sent, it waits either for
           deadline expire or until count probes are answered or for some
           error notification from network.

       -W timeout
           Time to wait for a response, in seconds. The option affects only
           timeout in absence of any responses, otherwise ping waits for two
           RTTs.

       When using ping for fault isolation, it should first be run on the
       local host, to verify that the local network interface is up and
       running. Then, hosts and gateways further and further away should be
       “pinged”. Round-trip times and packet loss statistics are computed.
       If duplicate packets are received, they are not included in the
       packet loss calculation, although the round trip time of these
       packets is used in calculating the minimum/average/maximum/mdev
       round-trip time numbers.

       Median deviation (mdev), essentially an average of how far each ping
       RTT is from the mean RTT. The higher mdev is, the more variable the
       RTT is (over time). With a high RTT variability, you will have speed
       issues with bulk transfers (they will take longer than is strictly
       speaking necessary, as the variability will eventually cause the
       sender to wait for ACKs) and you will have middling to poor VoIP
       quality.

       When the specified number of packets have been sent (and received) or
       if the program is terminated with a SIGINT, a brief summary is
       displayed. Shorter current statistics can be obtained without
       termination of process with signal SIGQUIT.

       If ping does not receive any reply packets at all it will exit with
       code 1. If a packet count and deadline are both specified, and fewer
       than count packets are received by the time the deadline has arrived,
       it will also exit with code 1. On other error it exits with code 2.
       Otherwise it exits with code 0. This makes it possible to use the
       exit code to see if a host is alive or not.

       This program is intended for use in network testing, measurement and
       management. Because of the load it can impose on the network, it is
       unwise to use ping during normal operations or from automated
       scripts.

ICMP PACKET DETAILS         top

       An IP header without options is 20 bytes. An ICMP ECHO_REQUEST packet
       contains an additional 8 bytes worth of ICMP header followed by an
       arbitrary amount of data. When a packetsize is given, this indicated
       the size of this extra piece of data (the default is 56). Thus the
       amount of data received inside of an IP packet of type ICMP
       ECHO_REPLY will always be 8 bytes more than the requested data space
       (the ICMP header).

       If the data space is at least of size of struct timeval ping uses the
       beginning bytes of this space to include a timestamp which it uses in
       the computation of round trip times. If the data space is shorter, no
       round trip times are given.

DUPLICATE AND DAMAGED PACKETS         top

       ping will report duplicate and damaged packets. Duplicate packets
       should never occur, and seem to be caused by inappropriate link-level
       retransmissions. Duplicates may occur in many situations and are
       rarely (if ever) a good sign, although the presence of low levels of
       duplicates may not always be cause for alarm.

       Damaged packets are obviously serious cause for alarm and often
       indicate broken hardware somewhere in the ping packet's path (in the
       network or in the hosts).

TRYING DIFFERENT DATA PATTERNS         top

       The (inter)network layer should never treat packets differently
       depending on the data contained in the data portion. Unfortunately,
       data-dependent problems have been known to sneak into networks and
       remain undetected for long periods of time. In many cases the
       particular pattern that will have problems is something that doesn't
       have sufficient “transitions”, such as all ones or all zeros, or a
       pattern right at the edge, such as almost all zeros. It isn't
       necessarily enough to specify a data pattern of all zeros (for
       example) on the command line because the pattern that is of interest
       is at the data link level, and the relationship between what you type
       and what the controllers transmit can be complicated.

       This means that if you have a data-dependent problem you will
       probably have to do a lot of testing to find it. If you are lucky,
       you may manage to find a file that either can't be sent across your
       network or that takes much longer to transfer than other similar
       length files. You can then examine this file for repeated patterns
       that you can test using the -p option of ping.

TTL DETAILS         top

       The TTL value of an IP packet represents the maximum number of IP
       routers that the packet can go through before being thrown away. In
       current practice you can expect each router in the Internet to
       decrement the TTL field by exactly one.

       The TCP/IP specification states that the TTL field for TCP packets
       should be set to 60, but many systems use smaller values (4.3 BSD
       uses 30, 4.2 used 15).

       The maximum possible value of this field is 255, and most Unix
       systems set the TTL field of ICMP ECHO_REQUEST packets to 255. This
       is why you will find you can “ping” some hosts, but not reach them
       with telnet(1) or ftp(1).

       In normal operation ping prints the TTL value from the packet it
       receives. When a remote system receives a ping packet, it can do one
       of three things with the TTL field in its response:

           · Not change it; this is what Berkeley Unix systems did before
           the 4.3BSD Tahoe release. In this case the TTL value in the
           received packet will be 255 minus the number of routers in the
           round-trip path.

           · Set it to 255; this is what current Berkeley Unix systems do.
           In this case the TTL value in the received packet will be 255
           minus the number of routers in the path from the remote system to
           the pinging host.

           · Set it to some other value. Some machines use the same value
           for ICMP packets that they use for TCP packets, for example
           either 30 or 60. Others may use completely wild values.

BUGS         top

           · Many Hosts and Gateways ignore the RECORD_ROUTE option.

           · The maximum IP header length is too small for options like
           RECORD_ROUTE to be completely useful. There's not much that can
           be done about this, however.

           · Flood pinging is not recommended in general, and flood pinging
           the broadcast address should only be done under very controlled
           conditions.

SEE ALSO         top

       netstat(1), ifconfig(8).

HISTORY         top

       The ping command appeared in 4.3BSD.

       The version described here is its descendant specific to Linux.

       As of version s20150815, the ping6 binary doesn't exist anymore. It
       has been merged into ping. Creating a symlink named ping6 pointing to
       ping will result in the same funcionality as before.

SECURITY         top

       ping requires CAP_NET_RAW capability to be executed 1) if the program
       is used for non-echo queries (See -N option), or 2) if kernel does
       not support non-raw ICMP sockets, or 3) if the user is not allowed to
       create an ICMP echo socket. The program may be used as set-uid root.

AVAILABILITY         top

       ping is part of iputils package.

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
       about the project can be found at ⟨http://www.skbuff.net/iputils/⟩.
       If you have a bug report for this manual page, send it to
       yoshfuji@skbuff.net, netdev@vger.kernel.org.  This page was obtained
       from the project's upstream Git repository 
       ⟨https://github.com/iputils/iputils.git⟩ on 2017-09-15.  If you dis‐
       cover any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

iputils s20161105                                                    PING(8)

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