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.Dd May 17, 1998
.Dt NDP 8
.Os
.\"
.Sh NAME
.Nm ndp
.Nd control/diagnose IPv6 neighbor discovery protocol
.\"
.Sh SYNOPSIS
.Nm
.Fl a
.Op Fl nt
.Nm
.Fl A Ar wait
.Op Fl nt
.Nm
.Fl c
.Op Fl nt
.Nm
.Fl d
.Op Fl nt
.Ar hostname
.Nm
.Fl f
.Op Fl nt
.Ar filename
.Nm
.Fl H
.Nm
.Fl I
.Op Cm delete | Ar interface
.Nm
.Fl i
.Ar interface
.Op Ar flags...
.Nm
.Fl p
.Nm
.Fl P
.Nm
.Fl r
.Nm
.Fl R
.Nm
.Fl s
.Op Fl nt
.Ar nodename
.Ar ether_addr
.Op Li temp
.Op Li proxy
.\"
.Sh DESCRIPTION
The
.Nm
utility manipulates the address mapping table
used by Neighbor Discovery Protocol (NDP).
.Bl -tag -width Ds
.It Fl a
Dump the currently existing NDP entries.
.It Fl A Ar wait
Repeat
.Fl a
(dump NDP entries)
every
.Ar wait
seconds.
.It Fl c
Erase all the NDP entries.
.It Fl d
Delete specified NDP entry.
.It Fl f
Parse the file specified by
.Ar filename .
.It Fl H
Harmonize consistency between the routing table and the default router
list; install the top entry of the list into the kernel routing table.
.It Fl I Op Cm delete | Ar interface
Shows or specifies the default interface used as the default route when
there is no default router.
If no argument is given to the option,
the current default interface will be shown.
If an
.Ar interface
is specified, the interface will be used as the default.
If a special keyword
.Ic delete
is specified, the current default interface will be deleted from the kernel.
.It Fl i Ar interface Op Ar flags...
View ND information for the specified interface.
If additional arguments
.Ar flags
are given,
.Nm
sets or clears the specified flags for the interface.
Possible flags are as follows.
All of the flags can begin with the
special character
.Ql - ,
which means the flag should be cleared.
.\"
.Bl -tag -width Ds -compact
.It Xo
.Ic nud
.Xc
turn on or off NUD (Neighbor Unreachability Detection) on the
interface.
NUD is usually turned on by default.
.It Xo
.Ic accept_rtadv
.Xc
Specify whether or not to accept Router Advertisement messages
received on the
.Ar interface .
Note that the kernel does not accept Router Advertisement messages
unless the
.Va net.inet6.ip6.accept_rtadv
variable is non-0, even if the flag is on.
This flag is set to 1 by default.
.El
.It Fl n
Do not try to resolve numeric address to hostname.
.It Fl p
Show prefix list.
.It Fl P
Flush all the entries in the prefix list.
.It Fl r
Show default router list.
.It Fl R
Flush all the entries in the default router list.
.It Fl s
Register an NDP entry for a node.
The entry will be permanent unless the word
.Li temp
is given in the command.
If the word
.Li proxy
is given, this system will act as a proxy NDP server,
responding to requests for
.Ar hostname
even though the host address is not its own.
.It Fl t
Print timestamp on each entries,
to make it possible to merge output with
.Xr tcpdump 1 .
Most useful when used with
.Fl A .
.El
.\"
.Sh DIAGNOSTICS
The
.Nm
utility will exit with 0 on success, and non-zero on errors.
.\"
.Sh SEE ALSO
.Xr arp 8
.\"
.Sh HISTORY
The
.Nm
utility first appeared in WIDE Hydrangea IPv6 protocol stack kit.
.\"
.\" .Sh BUGS
.\" (to be written)