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NDP(8)                  FreeBSD System Manager's Manual                 NDP(8)

     ndp - control/diagnose IPv6 neighbor discovery protocol

     ndp [-nt] hostname
     ndp [-nt] -a | -c | -p
     ndp [-nt] -r
     ndp [-nt] -H | -P | -R
     ndp [-nt] -A wait
     ndp [-nt] -d hostname
     ndp [-nt] -f filename
     ndp [-nt] -i interface [expressions ...]
     ndp [-nt] -I [interface | delete]
     ndp [-nt] -s nodename etheraddr [temp] [proxy]

     The ndp utility manipulates the address mapping table used by the
     Neighbor Discovery Protocol (NDP).

     -a      Dump the currently existing NDP entries.  The following
             information will be printed:

             Neighbor  IPv6 address of the neighbor.

             Linklayer Address
                       Linklayer address of the neighbor.  It could be
                       ``(incomplete)'' when the address is not available.

             Netif     Network interface associated with the neighbor cache

             Expire    The time until expiry of the entry.  The entry could
                       become ``permanent'', in which case it will never

             S         State of the neighbor cache entry, as a single letter:

                       N       Nostate
                       W       Waitdelete
                       I       Incomplete
                       R       Reachable
                       S       Stale
                       D       Delay
                       P       Probe
                       ?       Unknown state (should never happen).

             Flags     Flags on the neighbor cache entry, in a single letter.
                       They are: Router, proxy neighbor advertisement (``p'').
                       The field could be followed by a decimal number, which
                       means the number of NS probes the node has sent during
                       the current state.

     -A wait
             Repeat -a (dump NDP entries) every wait seconds.

     -c      Erase all the NDP entries.

     -d      Delete specified NDP entry.

     -f      Parse the file specified by filename.

     -H      Harmonize consistency between the routing table and the default
             router list; install the top entry of the list into the kernel
             routing table.

     -I      Shows the default interface used as the default route when there
             is no default router.

     -I interface
             Specifies the default interface used as the default route when
             there is no default router.  The interface will be used as the

     -I delete
             The current default interface will be deleted from the kernel.

     -i interface [expressions ...]
             View ND information for the specified interface.  If additional
             arguments expressions are given, ndp sets or clears the flags or
             variables for the interface as specified in the expression.  Each
             expression should be separated by white spaces or tab characters.
             Possible expressions are as follows.  Some of the expressions can
             begin with the special character `-', which means the flag
             specified in the expression should be cleared.  Note that you
             need -- before -foo in this case.

             nud     Turn on or off NUD (Neighbor Unreachability Detection) on
                     the interface.  NUD is usually turned on by default.

                     Specify whether or not to accept Router Advertisement
                     messages received on the interface.  This flag is set by
                     net.inet6.ip6.accept_rtadv sysctl variable.

                     Specify whether or not to perform automatic link-local
                     address configuration on interface.  This flag is set by
                     net.inet6.ip6.auto_linklocal sysctl variable.

                     Prefer addresses on the interface as candidates of the
                     source address for outgoing packets.  The default value
                     of this flag is off.  For more details about the entire
                     algorithm of source address selection, see the
                     IMPLEMENTATION file supplied with the KAME kit.

                     The address on the outgoing interface is preferred by
                     source addess selection rule.  If this flag is set, stop
                     treating the address on the interface as special even
                     when the interface is outgoing interface.  The default
                     value of this flag is off.

                     Disable IPv6 operation on the interface.  When disabled,
                     the interface discards any IPv6 packets received on or
                     being sent to the interface.  In the sending case, an
                     error of ENETDOWN will be returned to the application.
                     This flag is typically set automatically in the kernel as
                     a result of a certain failure of Duplicate Address
                     Detection.  If the auto_linklocal per-interface flag is
                     set, automatic link-local address configuration is
                     performed again when this flag is cleared.

                     Specify the BaseReachbleTimer on the interface in

                     Specify the RetransTimer on the interface in millisecond.

                     Specify the Cur Hop Limit on the interface.

     -n      Do not try to resolve numeric addresses to hostnames.

     -p      Show prefix list.  The following information will be printed:

             if      The network interface associated with this prefix.

             flags   The status of the prefix, expressed by a combination of
                     the following letters:

                     A       This prefix can be used for stateless address
                     L, O    This prefix can be used for on-link
                             determination; that is, it can be used to
                             determine whether a given destination address is
                     D       There are no reachable routers advertising this

             vltime  Valid lifetime; the length of time for which the prefix
                     and a stateless autoconfigured address generated from
                     this prefix can be used for the source or destination
                     address of a packet.

             pltime  Preferred lifetime; the length of time for which the
                     prefix and a stateless autoconfigured address generated
                     from this prefix can be used by upper-layer protocols

             expire  This is the remaining time that the prefix is in the
                     valid state.

             ref     The number of kernel references held for this prefix.

     -P      Flush all the entries in the prefix list.

     -r      Show default router list.

     -R      Flush all the entries in the default router list.

     -s      Register an NDP entry for a node.  The entry will be permanent
             unless the word temp is given in the command.  If the word proxy
             is given, this system will act as a proxy NDP server, responding
             to requests for hostname even though the host address is not its

     -t      Print timestamp for each entry, to make it possible to merge the
             output with tcpdump(1).  Most useful when used with -A.

     The ndp utility exits 0 on success, and >0 if an error occurs.


     The ndp utility first appeared in the WIDE Hydrangea IPv6 protocol stack
     kit.  The -I auto_linklocal flag first appeared in FreeBSD 8.0.

FreeBSD 11.0-PRERELEASE        January 10, 2013        FreeBSD 11.0-PRERELEASE


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