Sends ICMPv6 ECHO_REQUEST packets to network hosts.

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 RFC2463.

ping6 [-dfHmnNqtvwW] [-a addrtype] [-b bufsize] [-c count] [-g gateway]
    [-h hoplimit] [-I interface] [-i wait] [-l preload] [-P policy]
    [-p pattern] [-S sourceaddr] [-s packetsize] [hops ...] host

Syntax

-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 unicast addresses from all of the responder's interfaces. 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	Returns only unicast addresses. With this character, the responder returns only anycast addresses. Note that the specification does not specify how to get responder's anycast addresses. This is an experimental option.

-b bufsize

Sets socket buffer size.

-c count

Stops after sending (and receiving) count ECHO_RESPONSE packets.

-d

Sets 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 net- work and should be used with caution.

-g gateway

Specifies to use gateway as the next hop to the destination. The gateway must be a neighbor of the sending node.

-H

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

-h hoplimit

Sets 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.

-m

By default, ping6 asks the kernel to fragment packets to fit into the minimum IPv6 MTU. The -m option suppresses the behavior in the following two levels:

• When the option is specified once, the behavior is disabled for unicast packets.
• When the option is more than once, it is disabled for both unicast and multicast packets.

-n

Numeric output only. No attempt will be made to look up 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 is computed based on given host, and is used as the final destination. Since node information multicast group is a link-local multicast group, outgoing interface 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" causes the sent packet to be filled with all ones.

-P policy

Policy specifies IPsec policy to be used for the probe.

-q

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

-S sourceaddr

Specifies the source address of request packets. The source address must be one of the unicast addresses of the sending node, and must be numeric.

-s packetsize

Specifies the number of data bytes to send. 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. If -t is specified, -s has no effect.

-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. If -w is specified, -s has no effect.

-W

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

hops

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

host

IPv6 address of the final destination node.

Remarks

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, 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.

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 would work; the following will send ICMPv6 echo request to 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

Requirements

Bugs

The ping6 utility is intentionally separate from ping.

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.

See Also

icmp6, inet6, ip6, ifconfig, netstat, ping, route, traceroute