ping(8) — Linux manual page

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 unless 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 every 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. Real
           number allowed with dot as a decimal separator (regardless
           locale setup). 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, an interface name or a VRF
           name. If interface is an address, it sets source address to
           specified interface address. If interface is an interface
           name, it sets source interface to specified interface. If
           interface is a VRF name, each packet is routed using the
           corresponding routing table; in this case, the -I option can
           be repeated to specify a source address. NOTE: For IPv6, when
           doing ping to a link-local scope address, link specification
           (by the '%'-notation in destination, or by this option) can
           be used but it is no longer 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. Do not suppress DUP replies when pinging
           multicast address.

       -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. Real number allowed with dot as a decimal
           separator (regardless locale setup). 0 means infinite
           timeout.

       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.

       Population standard 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 indicates 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

       ip(8), ss(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 functionality 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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-27.)  If you discover 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 20210722                                                 PING(8)

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