PING(8)				    iputils			       PING(8)

NAME
       ping - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS
       ping [-aAbBdCDfhHLnOqrRUvV346] [-c count] [-e identifier]
	    [-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
       -3
	   RTT precision (do not round up the result time).

       -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. The default interval is
	   2 ms, for more info see option -i. 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.

       -C
	   Call connect() syscall on socket creation.

       -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.

       -e identifier
	   Set the identification field of ECHO_REQUEST. Value 0 implies using
	   raw socket (not supported on ICMP datagram socket). The value of
	   the field may be printed with -v option.

       -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.

       -H
	   Force DNS name resolution for the output. Useful for numeric
	   destination, or -f option, which by default do not perform it. It
	   can also help to workaround DNS resolution problems. Override
	   previously defined -n option. See also IPUTILS_PING_PTR_LOOKUP
	   environment variable.

       -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 2 ms. Broadcast and multicast ping have even
	   higher limitation for regular user: minimum is 1 sec.

       -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. CAP_NET_ADMIN or CAP_NET_RAW (since
	   Linux 5.17) capability is required, see socket(7).

       -M pmtudisc_opt
	   Select Path MTU Discovery strategy.	pmtudisc_option may be either
	   do (set DF flag but subject to PMTU checks by kernel, packets too
	   large will be rejected), want (do PMTU discovery, fragment locally
	   when packet size is large), probe (set DF flag and bypass PMTU
	   checks, useful for probing), or dont (do not set DF flag).

       -N nodeinfo_option
	   IPv6 only. Send IPv6 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 (no reverse DNS resolution). This is the
	   default for numeric destination or -f option. Override previously
	   defined -H option. See also IPUTILS_PING_PTR_LOOKUP environment
	   variable.

       -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. The maximum allowed value is 65507 for
	   IPv4 (65467 when -R or -T or Intermediate hops) or 65527 for IPv6,
	   but most systems limit this to a smaller, system-dependent number.

       -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.

       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.

ENVIRONMENT
       IPUTILS_PING_PTR_LOOKUP environment variable set to 0 disable reverse
       DNS resolution (PTR lookup) by default. It will be overrided by -H or
       -n option.

EXIT STATUS
       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.

IPV6 LINK-LOCAL DESTINATIONS
       For IPv6, when the destination address has link-local scope and ping is
       using ICMP datagram sockets, the output interface must be specified.
       When ping is using raw sockets, it is not strictly necessary to specify
       the output interface but it should be done to avoid ambiguity when
       there are multiple possible output interfaces.

       There are two ways to specify the output interface:

       • using the % notation
	   The destination address is postfixed with % and the output
	   interface name or ifindex, for example:

	   ping fe80::5054:ff:fe70:67bc%eth0

	   ping fe80::5054:ff:fe70:67bc%2

       • using the -I option
	   When using ICMP datagram sockets, this method is supported since
	   the following kernel versions: 5.17, 5.15.19, 5.10.96, 5.4.176,
	   4.19.228, 4.14.265. Also it is not supported on musl libc.

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 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
       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).

ID COLLISIONS
       Unlike TCP and UDP, which use port to uniquely identify the recipient
       to deliver data, ICMP uses identifier field (ID) for identification.
       Therefore, if on the same machine, at the same time, two ping processes
       use the same ID, echo reply can be delivered to a wrong recipient. This
       is a known problem due to the limited size of the 16-bit ID field. That
       is a historical limitation of the protocol that cannot be fixed at the
       moment unless we encode an ID into the ping packet payload.  ping
       prints DIFFERENT ADDRESS error and packet loss is negative.

       ping uses PID to get unique number. The default value of
       /proc/sys/kernel/pid_max is 32768. On the systems that use ping heavily
       and with pid_max greater than 65535 collisions are bound to happen.

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 TTL field for TCP packets may take various values. The maximum
       possible value of this field is 255, a recommended initial value is 64.
       For more information, see the TCP/Lower-Level Interface section of
       RFC9293.

       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
	   • 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
       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 functionality 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 when the identification
       field set to 0 for ECHO_REQUEST (see -e), or 2) if kernel does not
       support ICMP datagram 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 20250605						       PING(8)