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.Dd Sep 02, 2015
.Dt NDP 1M
.Os
.Sh NAME
.Nm ndp
.Nd manipulate IPv6 Neighbor Discovery Protocol mappings
.Sh SYNOPSIS
.Nm
.Op Fl n
.Fl a
.Nm
.Op Fl n
.Fl A Ar period
.Nm
.Op Fl n
.Op Fl i Ar iface
.Ar hostname
.Nm
.Op Fl n
.Op Fl i Ar iface
.Fl d Ar hostname
.Nm
.Op Fl n
.Op Fl i Ar iface
.Fl f Ar filename
.Nm
.Op Fl n
.Op Fl i Ar iface
.Fl s Ar hostname lladdr
.Op Cm temp
.Op Cm any
.Op Cm router
.Sh DESCRIPTION
The
.Nm
command displays and modifies the IPv6-to-MAC address translation
tables used by the Neighbor Discovery Protocol
.Po see Xr ndp 7P Pc .
.Pp
Given just a hostname,
.Nm
will display the current entry. Note that when getting, setting or deleting,
if a hostname refers to multiple IPv6 addresses, the operation will apply to
all of them.
.Pp
The NDP translation tables can be modified with
.Fl d ,
.Fl s ,
or
.Fl f .
These flags can only be used when
.Nm
is given the
.Sy PRIV_SYS_NET_CONFIG
privilege. See
.Xr privileges 5
for further information.
.Pp
Note that NDP entries for IPMP (IP Network Multipathing) data and
test addresses are managed by the kernel and therefore cannot be
modified or deleted.
.Sh OPTIONS
.Bl -tag -width 6m
.It Fl a
Display all NDP entries. Entries can be one of several types:
.Bl -tag -offset indent -width 7n
.It Sy dynamic
This is a normal NDP mapping and will eventually expire. This is the most
common type of mapping for non-local addresses that will be displayed.
.It Sy local
The IPv6 address is local to the machine.
.It Sy other
The mapping is a multicast or broadcast address, or the system is acting
as proxy for the address.
.It Sy static
The mapping is static and will not be removed from the machine over time.
.El
.Pp
Entries also exist in one of the following states:
.Bl -tag -offset indent -width 12m
.It Sy INCOMPLETE
Address resolution is in progress
.It Sy REACHABLE
This address has recently been reachable
.It Sy STALE
This address may be unreachable
.It Sy DELAY
Waiting to send out reachability probes
.It Sy PROBE
Sending out probes for the address
.It Sy UNREACHABLE
The address is unreachable, and will be deleted
.It Sy UNKNOWN
The state of the entry is unknown
.El
.Pp
Using the
.Fl a
flag is equivalent to:
.sp
.Dl # netstat -p -f inet6
.sp
If
.Fl n
is passed to
.Nm ,
then it will be passed along to
.Nm netstat .
.It Fl A
Display all NDP entries every
.Ar period
seconds.
.It Fl d
Delete NDP mappings for the host called
.Ar hostname .
.It Fl f
Read in the lines from
.Ar filename
and use each one to set a mapping. The syntax of each line is the
same as the arguments to
.Fl s .
Lines beginning with `#' will be ignored.
.It Fl i
By default,
.Nm
will use the routing table to determine the appropriate interface to place the
mapping on. This flag allows forcing a specific interface
.Ar iface .
This argument will be ignored when using the
.Fl a
or
.Fl A
flags.
.It Fl n
Disable the default translation of numeric IP addresses to host names when
printing.
.It Fl s
Add or update an NDP mapping, and set the desired properties for the entry. The
list of flags should be the full set of flags desired on the entry, i.e., not
listing a flag will remove it if it already exists. The following flags can be
used:
.Bl -tag -offset indent -width Ds
.It Cm temp
The entry should be temporary and eventually expire like a normal NDP
entry. By default, all entries created with the
.Nm
command are static, and will not be deleted. To make a static entry temporary,
it should be deleted and recreated with the
.Cm temp
flag.
.It Cm any
The address should be treated like an anycast address. This will prevent the
system from sending Neighbor Advertisements with the Override flag.
.It Cm router
The address should be treated like a router address. This cause the system to
send Neighbor Advertisements with the Router flag.
.El
.El
.Sh EXAMPLES
.Ss Example 1: Setting a mapping
To create a temporary mapping for an address:
.Bd -literal -offset indent
# ndp -s fd00::1 90:b8:d0:4b:c7:3b temp
.Ed
.Ss Example 2: Getting a mapping
An entry can be fetched via its IP address:
.Bd -literal -offset indent
# ndp fd00::1
fd00::1 (fd00::1) at 90:b8:d0:4b:c7:3b temp
.Ed
.sp
Or via a name that resolves to that address:
.Bd -literal -offset indent
# echo fd00::1 epicac >> /etc/hosts
# echo fd00::2 epicac >> /etc/hosts
# ndp epicac
fd00::1 (epicac) at 90:b8:d0:4b:c7:3b temp
fd00::2 (epicac) -- no entry
.Ed
.Ss Example 3: Deleting a mapping
An entry can be removed with the
.Fl d
flag:
.Bd -literal -offset indent
# ndp -d fd00::1
.Ed
.sp
Attempting to remove it again will print an error message:
.Bd -literal -offset indent
# ndp -d fd00::1
ndp: No entry for fd00::1
.Ed
.Sh STABILITY
The command line options for this command are stable, but the output format
and diagnostic messages are not.
.Sh SEE ALSO
.Xr arp 1M ,
.Xr ifconfig 1M ,
.Xr netstat 1M ,
.Xr attributes 5 ,
.Xr privileges 5 ,
.Xr ndp 7P