.\"	$OpenBSD: ndp.8,v 1.21 2004/09/15 22:52:00 jmc Exp $
.\"	$KAME: ndp.8,v 1.28 2002/07/17 08:46:33 itojun Exp $
.\"
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.\"
.Dd May 17, 1998
.Dt NDP 8
.Os
.\"
.Sh NAME
.Nm ndp
.Nd control/diagnose IPv6 Neighbor Discovery Protocol (NDP)
.\"
.Sh SYNOPSIS
.Nm ndp
.Op Fl nt
.Ar hostname
.Nm ndp
.Op Fl nt
.Fl a | c | p
.Nm ndp
.Op Fl nt
.Fl r
.Nm ndp
.Op Fl nt
.Fl H | P | R
.Nm ndp
.Op Fl nt
.Fl A Ar wait
.Nm ndp
.Op Fl nt
.Fl d Ar hostname
.Nm ndp
.Op Fl nt
.Fl f Ar filename
.Nm ndp
.Op Fl nt
.Fl i
.Ar interface
.Op Ar flags ...
.Nm ndp
.Op Fl nt
.Fl I Op Ar interface | Ic delete
.Nm ndp
.Op Fl nt
.Fl s Ar nodename etheraddr
.Op Ic temp
.Op Ic proxy
.\"
.Sh DESCRIPTION
The
.Nm
command manipulates the address mapping table
used by the Neighbor Discovery Protocol (NDP).
.Bl -tag -width Ds
.It Fl A Ar wait
Repeat
.Fl a
.Pq dump NDP entries
every
.Ar wait
seconds.
.It Fl a
Dump the currently existing NDP entries.
The following information will be printed:
.Bl -tag -width NeighborXX
.It Neighbor
IPv6 address of the neighbor.
.It Linklayer Address
Linklayer address of the neighbor.
It could be
.Dq Li (incomplete)
when the address is not available.
.It Netif
Network interface associated with the neighbor cache entry.
.It Expire
The time until expiry of the entry.
The entry could become
.Dq Li permanent ,
in which case it will never expire.
.It S
State of the neighbor cache entry, as a single letter:
.Pp
.Bl -tag -width indent -compact
.It N
Nostate
.It W
Waitdelete
.It I
Incomplete
.It R
Reachable
.It S
Stale
.It D
Delay
.It P
Probe
.It \&?
Unknown state (should never happen).
.El
.It Flags
Flags on the neighbor cache entry, in a single letter.
They are: Router, proxy neighbor advertisement
.Pq Dq 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.
.El
.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
Shows the default interface used as the default route when
there is no default router.
.It Fl I Ar interface
Specifies the default interface used as the default route when
there is no default router.
The
.Ar interface
will be used as the default.
.It Fl I Ic delete
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.
Each flag should be separated by whitespace or tab characters.
Possible flags are as follows.
All of the flags can begin with the
special character
.Ql - ,
which means the flag should be cleared.
Note that you need
.Fl -
before
.Fl foo
in this case.
.\"
.Bl -tag -width Ds
.It Ic nud
Turn on or off NUD (Neighbor Unreachability Detection) on the
interface.
NUD is usually turned on by default.
.It Ic accept_rtadv
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
.Li net.inet6.ip6.accept_rtadv
variable is non-0, even if the flag is on.
This flag is set to 1 by default.
See
.Xr sysctl 8
and
.Xr sysctl.conf 5
for further details on how to set the
.Li net.inet6.ip6.accept_rtadv
variable.
.\".It Xo
.\".Ic prefer_source
.\".Xc
.\"Prefer addresses on the
.\".Ar 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
.\".Pa IMPLEMENTATION
.\"file supplied with the KAME kit.
.El
.It Fl n
Do not try to resolve numeric addresses to hostnames.
.It Fl P
Flush all the entries in the prefix list.
.It Fl p
Show prefix list.
.It Fl R
Flush all the entries in the default router list.
.It Fl r
Show default router list.
.It Fl s
Register a NDP entry for a node.
The entry will be permanent unless the word
.Ic temp
is given in the command.
If the word
.Ic 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 entry,
making it possible to merge output with
.Xr tcpdump 8 .
Most useful when used with
.Fl A .
.El
.\"
.Sh RETURN VALUES
The
.Nm
command exits with 0 on success, and non-zero on errors.
.\"
.Sh SEE ALSO
.Xr ip6 4 ,
.Xr sysctl.conf 5 ,
.Xr arp 8 ,
.Xr sysctl 8 ,
.Xr tcpdump 8
.\"
.Sh HISTORY
The
.Nm
command first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
.\"
.\" .Sh BUGS
.\" (to be written)