.\"	$KAME: ndp.8,v 1.28 2002/07/17 08:46:33 itojun Exp $
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.\" $FreeBSD$
.\"
.Dd May 9, 2014
.Dt NDP 8
.Os
.\"
.Sh NAME
.Nm ndp
.Nd control/diagnose IPv6 neighbor discovery protocol
.\"
.Sh SYNOPSIS
.Nm
.Op Fl nt
.Ar hostname
.Nm
.Op Fl nt
.Fl a | c | p
.Nm
.Op Fl nt
.Fl r
.Nm
.Op Fl nt
.Fl H | P | R
.Nm
.Op Fl nt
.Fl A Ar wait
.Nm
.Op Fl nt
.Fl d Ar hostname
.Nm
.Op Fl nt
.Fl f Ar filename
.Nm
.Op Fl nt
.Fl i
.Ar interface
.Op Ar expressions ...
.Nm
.Op Fl nt
.Fl I Op Ar interface | Li delete
.Nm
.Op Fl nt
.Fl s Ar nodename etheraddr
.Op Li temp
.Op Li proxy
.\"
.Sh DESCRIPTION
The
.Nm
utility manipulates the address mapping table
used by the Neighbor Discovery Protocol (NDP).
.Bl -tag -width indent
.It Fl a
Dump the currently existing NDP entries.
The following information will be printed:
.Bl -tag -width "Neighbor"
.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 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 Ar filename
Cause the file
.Ar filename
to be read and multiple entries to be set in the
.Tn NDP
table.
Entries
in the file should be of the form
.Pp
.Bd -ragged -offset indent -compact
.Ar hostname ether_addr
.Op Cm temp
.Op Cm proxy
.Ed
.Pp
with argument meanings as given above.
Leading whitespace and empty lines are ignored.
A
.Ql #
character will mark the rest of the line as a comment.
.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 Li delete
The current default interface will be deleted from the kernel.
.It Fl i Ar interface Op Ar expressions ...
View ND information for the specified interface.
If additional arguments
.Ar expressions
are given,
.Nm
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
.Ql - ,
which means the flag specified in the expression should be cleared.
Note that you need
.Fl -
before
.Fl foo
in this case.
.\"
.Bl -tag -width indent
.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 .
This flag is set by
.Va net.inet6.ip6.accept_rtadv
sysctl variable.
.It Ic auto_linklocal
Specify whether or not to perform automatic link-local address configuration
on
.Ar interface .
This flag is set by
.Va net.inet6.ip6.auto_linklocal
sysctl variable.
.It Ic no_prefer_iface
The address on the outgoing interface is preferred by source addess
selection rule.
If this flag is set, stop treating the address on the
.Ar interface
as special even when the
.Ar interface
is outgoing interface.
The default value of this flag is off.
.It Ic disabled
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.
.It Ic basereachable Ns Li = Ns Pq Ar number
Specify the BaseReachbleTimer on the interface in millisecond.
.It Ic retrans Ns Li = Ns Pq Ar number
Specify the RetransTimer on the interface in millisecond.
.It Ic curhlim Ns Li = Ns Pq Ar number
Specify the Cur Hop Limit on the interface.
.El
.It Fl n
Do not try to resolve numeric addresses to hostnames.
.It Fl p
Show prefix list.
The following information will be printed:
.Bl -tag -width indent
.It Cm if
The network interface associated with this prefix.
.It Cm flags
The status of the prefix, expressed by a combination of the following
letters:
.Pp
.Bl -tag -width indent -compact
.It Cm A
This prefix can be used for stateless address autoconfiguration.
.It Cm L, Cm O
This prefix can be used for on-link determination; that is, it can be
used to determine whether a given destination address is on-link.
.It Cm D
There are no reachable routers advertising this prefix.
.El
.It Cm 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.
.It Cm 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 unrestrictedly.
.It Cm expire
This is the remaining time that the prefix is in the valid state.
.It Cm ref
The number of kernel references held for this prefix.
.El
.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 for each entry,
to make it possible to merge the output with
.Xr tcpdump 1 .
Most useful when used with
.Fl A .
.El
.\"
.Sh EXIT STATUS
.Ex -std
.\"
.Sh SEE ALSO
.Xr arp 8
.\"
.Sh HISTORY
The
.Nm
utility first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
The
.Fl I Ar auto_linklocal
flag first appeared in
.Fx 8.0 .
.\"
.\" .Sh BUGS
.\" (to be written)