PING6(8)

NAME
ping6 - send ICMPv6 ECHO_REQUEST packets to network hosts

SYNOPSIS
ping6 [-dfHnNqRtvwW] [-a addrtype] [-b bufsiz] [-c count] [-h hoplimit] [-I interface] [-i wait] [-l preload] [-p pattern] [-S sourceaddr] [-s packetsize] [hops...] host

DESCRIPTION
The ping6 utility uses the ICMPv6 protocol's mandatory ICMP6_ECHO_REQUEST datagram to elicit an ICMP6_ECHO_REPLY from a host or gateway. ICMP6_ECHO_REQUEST datagrams (``pings'') have an IPv6 header, and ICMPv6 header formatted as documented in RFC 2463. The options are as follows:

-a addrtype
    Generate ICMPv6 Node Information Node Addresses query, rather than echo-request. addrtype must be a string constructed of the following characters.
    a   requests all the responder's unicast addresses. If the character is omitted, only those addresses which belong to the interface which has the responder's address are requests.
    c   requests responder's IPv4-compatible and IPv4-mapped addresses.
    g   requests responder's global-scope addresses.
    s   requests responder's site-local addresses.
    l   requests responder's link-local addresses.
    A   requests responder's anycast addresses. Without this character, the responder will return unicast addresses only. With this character, the responder will return anycast addresses only. Note that the specification does not specify how to get responder's anycast addresses. This is an experimental option.

-b bufsiz
    Set socket buffer size.

-c count
    Stop after sending (and receiving) count ECHO_RESPONSE packets.

-d  Set the SO_DEBUG option on the socket being used.

-f  Flood ping. Outputs packets as fast as they come back or one hundred times per second, whichever is more. 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. Only the super-user may use this option. This can be very hard on a network and should be used with caution.

-H  Specifies to try reverse-lookup of IPv6 addresses. The ping6 utility does not try reverse-lookup unless the option is specified.

-h hoplimit
    Set the IPv6 hoplimit.

-I interface
    Source packets with the given interface address. This flag applies if the ping destination is a multicast address, or link-local/site-local unicast address.

-i wait
    Wait wait seconds between sending each packet. The default is to wait for one second between each packet. This option is incompatible with the -f option.

-l preload
    If preload is specified, ping6 sends that many packets as fast as possible before falling into its normal mode of behavior. Only the super-user may use this option.

-n  Numeric output only. No attempt will be made to lookup symbolic names from addresses in the reply.

-N  Probe node information multicast group (ff02::2:xxxx:xxxx). host must be string hostname of the target (must not be a numeric IPv6 address). Node information multicast group will be computed based on given host, and will be used as the final destination. Since node information multicast group is a link-local multicast group, destination link needs to be specified by -I option.

-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.

-R  Make the kernel believe that the target host (or the first hop if you specify hops) is reachable, by injecting upper-layer reachability confirmation hint. The option is meaningful only if the target host (or the first hop) is a neighbor.

-S sourceaddr
    Specifies the source address of request packets. The source address must be one of the unicast addresses of the sending node. If the outgoing interface is specified by the -I option as well, sourceaddr needs to be an address assigned to the specified interface.

-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. You may need to specify -b as well to extend socket buffer size.

-t  Generate ICMPv6 Node Information supported query types query, rather than echo-request. -s has no effect if -t is specified.

-v  Verbose output. ICMP packets other than ECHO_RESPONSE that are received are listed.

-w  Generate ICMPv6 Node Information DNS Name query, rather than echo-request. -s has no effect if -w is specified.

-W  Same as -w, but with old packet format based on 03 draft. This option is present for backward compatibility. -s has no effect if -w is specified.

hops
    IPv6 addresses for intermediate nodes, which will be put into type 0 routing header.

host
    IPv6 address of the final destination node.

When using ping6 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 round-trip time statistics. 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, showing the number of packets sent and received, and the minimum, mean, maximum, and standard deviation of the round-trip times.

If ping6 receives a SIGINFO (see the status argument for stty(1)) signal, the current number of packets sent and received, and the minimum, mean, maximum, and standard deviation of the round-trip times will be written to the standard output in the same format as the standard completion message.

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 ping6 during normal operations or from automated scripts.

DUPLICATE AND DAMAGED PACKETS
The ping6 utility will report duplicate and damaged packets. Duplicate packets should never occur when pinging a unicast address, 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. Duplicates are expected when pinging a broadcast or multicast address, since they are not really duplicates but replies from different hosts to the same request.

Damaged packets are obviously serious cause for alarm and often indicate broken hardware somewhere in the ping6 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 does not have sufficient “transitions”, such as all ones or all zeros, or a pattern right at the edge, such as almost all zeros. It is not 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 cannot 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 ping6.

EXIT STATUS
The ping6 utility returns 0 on success (the host is alive), and non-zero if the arguments are incorrect or the host is not responding.

EXAMPLES
Normally, ping6 works just like ping(8) would work; the following will send ICMPv6 echo request to dst.foo.com.

    ping6 -n dst.foo.com

The following will probe hostnames for all nodes on the network link attached to wi0 interface. The address ff02::1 is named the link-local all-node multicast address, and the packet would reach every node on the network link.

    ping6 -w ff02::1%wi0

The following will probe addresses assigned to the destination node, dst.foo.com.

    ping6 -a agl dst.foo.com

SEE ALSO
netstat(1), icmp6(4), inet6(4), ip6(4), ifconfig(8), ping(8), routed(8), traceroute(8), traceroute6(8) A. Conta, S. Deering, Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification, RFC 2463, December 1998. Matt Crawford, IPv6 Node Information Queries, draft-ietf-ipngwg-icmp-name-lookups-07.txt, August 2000, work in progress material.

HISTORY
The ping(8) command appeared in 4.3BSD. The ping6 utility with IPv6 support first appeared in WIDE Hydrangea IPv6 protocol stack kit.

IPv6 support based on the KAME Project (http://www.kame.net/) stack was initially integrated into FreeBSD 4.0

BUGS
There have been many discussions on why we separate ping6 and ping(8). Some people argued that it would be more convenient to uniform the ping command for both IPv4 and IPv6. The followings are an answer to the request.

From a developer's point of view: since the underling raw sockets API is totally different between IPv4 and IPv6, we would end up having two types of code base. There would actually be less benefit to uniform the two commands into a single command from the developer's standpoint.

From an operator's point of view: unlike ordinary network applications like remote login tools, we are usually aware of address family when using network management tools. We do not just want to know the reachability to the host, but want to know the reachability to the host via a particular network protocol such as IPv6. Thus, even if we had a unified ping(8) command for both IPv4 and IPv6, we would usually type a -6 or -4 option (or something like those) to specify the particular address family. This essentially means that we have two different commands.