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NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | AUTHOR | COLOPHON |
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IP-NEIGHBOUR(8) Linux IP-NEIGHBOUR(8)
ip-neighbour - neighbour/arp tables management.
ip [ OPTIONS ] neigh { COMMAND | help }
ip neigh { add | del | change | replace } { ADDR [ lladdr LLADDR ]
[ nud STATE ] | proxy ADDR } [ dev DEV ] [ router ] [ use
] [ managed ] [ extern_learn ] [ extern_valid ]
ip neigh { show | flush } [ proxy ] [ to PREFIX ] [ dev DEV ] [
nud STATE ] [ vrf NAME ] [ nomaster ]
ip neigh get ADDR dev DEV
STATE := { permanent | noarp | stale | reachable | none |
incomplete | delay | probe | failed }
The ip neigh command manipulates neighbour objects that establish
bindings between protocol addresses and link layer addresses for
hosts sharing the same link. Neighbour entries are organized into
tables. The IPv4 neighbour table is also known by another name -
the ARP table.
The corresponding commands display neighbour bindings and their
properties, add new neighbour entries and delete old ones.
ip neighbour add
add a new neighbour entry
ip neighbour change
change an existing entry
ip neighbour replace
add a new entry or change an existing one
These commands create new neighbour records or update
existing ones.
to ADDRESS (default)
the protocol address of the neighbour. It is either
an IPv4 or IPv6 address.
dev NAME
the interface to which this neighbour is attached.
proxy indicates whether we are proxying for this neighbour
entry
router indicates whether neighbour is a router
use this neigh entry is in "use". This option can be
used to indicate to the kernel that a controller is
using this dynamic entry. If the entry does not
exist, the kernel will resolve it. If it exists, an
attempt to refresh the neighbor entry will be
triggered.
managed
this neigh entry is "managed". This option can be
used to indicate to the kernel that a controller is
using this dynamic entry. In contrast to "use", if
the entry does not exist, the kernel will resolve it
and periodically attempt to auto-refresh the
neighbor entry such that it remains in resolved
state when possible.
extern_learn
this neigh entry was learned externally. This option
can be used to indicate to the kernel that this is a
controller learnt dynamic entry. Kernel will not gc
such an entry.
extern_valid
this neigh entry was learned and determined to be
valid externally. The kernel will not remove or
invalidate the entry, but it can probe the entry and
notify user space when the entry becomes reachable.
The kernel will return the entry to stale state if
it did not receive a confirmation after probing the
entry.
lladdr LLADDRESS
the link layer address of the neighbour. LLADDRESS
can also be null.
nud STATE
the state of the neighbour entry. nud is an
abbreviation for 'Neighbour Unreachability
Detection'. The state can take one of the following
values:
permanent
the neighbour entry is valid forever and can
be only be removed administratively.
noarp the neighbour entry is valid. No attempts to
validate this entry will be made but it can
be removed when its lifetime expires.
reachable
the neighbour entry is valid until the
reachability timeout expires.
stale the neighbour entry is valid but suspicious.
This option to ip neigh does not change the
neighbour state if it was valid and the
address is not changed by this command.
none this is a pseudo state used when initially
creating a neighbour entry or after trying to
remove it before it becomes free to do so.
incomplete
the neighbour entry has not (yet) been
validated/resolved.
delay neighbor entry validation is currently
delayed.
probe neighbor is being probed.
failed max number of probes exceeded without
success, neighbor validation has ultimately
failed.
ip neighbour delete
delete a neighbour entry
The arguments are the same as with ip neigh add, except
that lladdr and nud are ignored.
Warning: Attempts to delete or manually change a noarp
entry created by the kernel may result in unpredictable
behaviour. Particularly, the kernel may try to resolve
this address even on a NOARP interface or if the address is
multicast or broadcast.
ip neighbour show
list neighbour entries
to ADDRESS (default)
the prefix selecting the neighbours to list.
dev NAME
only list the neighbours attached to this device.
vrf NAME
only list the neighbours for given VRF.
nomaster
only list neighbours attached to an interface with
no master.
proxy list neighbour proxies.
unused only list neighbours which are not currently in use.
nud STATE
only list neighbour entries in this state.
NUD_STATE takes values listed below or the special
value all which means all states. This option may
occur more than once. If this option is absent, ip
lists all entries except for none and noarp.
ip neighbour flush
flush neighbour entries
This command has the same arguments as show. The
differences are that it does not run when no arguments are
given, and that the default neighbour states to be flushed
do not include permanent and noarp.
With the -statistics option, the command becomes verbose.
It prints out the number of deleted neighbours and the
number of rounds made to flush the neighbour table. If the
option is given twice, ip neigh flush also dumps all the
deleted neighbours.
ip neigh get
lookup a neighbour entry to a destination given a device
proxy indicates whether we should lookup a proxy neighbour
entry
to ADDRESS (default)
the prefix selecting the neighbour to query.
dev NAME
get neighbour entry attached to this device.
ip neighbour
Shows the current neighbour table in kernel.
ip neigh flush dev eth0
Removes entries in the neighbour table on device eth0.
ip neigh get 10.0.1.10 dev eth0
Performs a neighbour lookup in the kernel and returns a
neighbour entry.
ip(8)
Original Manpage by Michail Litvak <mci@owl.openwall.com>
This page is part of the iproute2 (utilities for controlling
TCP/IP networking and traffic) project. Information about the
project can be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
netdev@vger.kernel.org, shemminger@osdl.org. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-08.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
iproute2 20 Dec 2011 IP-NEIGHBOUR(8)
Pages that refer to this page: ip(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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