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IP-NEIGHBOUR(8) Linux IP-NEIGHBOUR(8)

NAME
ip-neighbour - neighbour/arp tables management.

SYNOPSIS
ip [ OPTIONS ] neigh { COMMAND | help }

ip neigh { add | del | change | replace } { ADDR [ lladdr LLADDR ] [ nud STATE ] | proxy ADDR
} [ dev DEV ] [ router ] [ extern_learn ]

ip neigh { show | flush } [ proxy ] [ to PREFIX ] [ dev DEV ] [ nud STATE ] [ vrf NAME ]

ip neigh get ADDR dev DEV

STATE := { permanent | noarp | stale | reachable | none | incomplete | delay | probe | failed
}

DESCRIPTION
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 ta‐
ble.

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

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.

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 Un‐
reachability Detection'. The state can take one of the following values:

permanent
the neighbour entry is valid forever and can be only be removed adminis‐
tratively.

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 ig‐
nored.

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.

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.

EXAMPLES
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.

phpMan > man > ip-neighbour(8)