ping4

PING(8)                             iputils                            PING(8)

NAME
       ping - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS
       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
       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
       -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. 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.

       -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.

       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
       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
       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
       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
       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:

           o 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.

           o 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.

           o 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
           o Many Hosts and Gateways ignore the RECORD_ROUTE option.

           o 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.

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

SEE ALSO
       ip(8), ss(8).

HISTORY
       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
       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
       ping is part of iputils package.

iputils s20190709                                                      PING(8)