.TH IP\-NEIGHBOUR 8 "20 Dec 2011" "iproute2" "Linux"

.SH "NAME"

ip-neighbour \- neighbour/arp tables management.

.SH "SYNOPSIS"

.sp

.ad l

.in +8

.ti -8

.B ip

.RI "[ " OPTIONS " ]"

.B neigh

.RI " { " COMMAND " | "

.BR help " }"

.sp

.ti -8

.BR "ip neigh" " { " add " | " del " | " change " | " replace " } { "

.IR ADDR " [ "

.B  lladdr

.IR LLADDR " ] [ "

.B nud

.IR STATE " ] |"

.B proxy

.IR ADDR " } [ "

.B  dev

.IR DEV " ] [ "

.BR router " ] [ "

.BR extern_learn " ]"

.ti -8

.BR "ip neigh" " { " show " | " flush " } [ " proxy " ] [ " to

.IR PREFIX " ] [ "

.B  dev

.IR DEV " ] [ "

.B  nud

.IR STATE " ] [ "

.B  vrf

.IR NAME " ] "

.ti -8

.IR STATE " := {"

.BR permanent " | " noarp " | " stale " | " reachable " | " none " |"

.BR incomplete " | " delay " | " probe " | " failed " }"

.SH DESCRIPTION

The

.B ip neigh

command manipulates

.I 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.

.P

The corresponding commands display neighbour bindings

and their properties, add new neighbour entries and delete old ones.

.TP

ip neighbour add

add a new neighbour entry

.TP

ip neighbour change

change an existing entry

.TP

ip neighbour replace

add a new entry or change an existing one

.RS

.PP

These commands create new neighbour records or update existing ones.

.TP

.BI to " ADDRESS " (default)

the protocol address of the neighbour. It is either an IPv4 or IPv6 address.

.TP

.BI dev " NAME"

the interface to which this neighbour is attached.

.TP

.BI proxy

indicates whether we are proxying for this neigbour entry

.TP

.BI router

indicates whether neigbour is a router

.TP

.BI 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.

.TP

.BI lladdr " LLADDRESS"

the link layer address of the neighbour.

.I LLADDRESS

can also be

.BR "null" .

.TP

.BI nud " STATE"

the state of the neighbour entry.

.B nud

is an abbreviation for 'Neighbour Unreachability Detection'.

The state can take one of the following values:

.RS

.TP

.B permanent

the neighbour entry is valid forever and can be only

be removed administratively.

.TP

.B noarp

the neighbour entry is valid. No attempts to validate

this entry will be made but it can be removed when its lifetime expires.

.TP

.B reachable

the neighbour entry is valid until the reachability

timeout expires.

.TP

.B stale

the neighbour entry is valid but suspicious.

This option to

.B ip neigh

does not change the neighbour state if it was valid and the address

is not changed by this command.

.TP

.B 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.

.TP

.B incomplete

the neighbour entry has not (yet) been validated/resolved.

.TP

.B delay

neighbor entry validation is currently delayed.

.TP

.B probe

neighbor is being probed.

.TP

.B failed

max number of probes exceeded without success, neighbor validation has

ultimately failed.

.RE

.RE

.TP

ip neighbour delete

delete a neighbour entry

.RS

.PP

The arguments are the same as with

.BR "ip neigh add" ,

except that

.B lladdr

and

.B nud

are ignored.

.PP

.B Warning:

Attempts to delete or manually change a

.B noarp

entry created by the kernel may result in unpredictable behaviour.

Particularly, the kernel may try to resolve this address even

on a

.B NOARP

interface or if the address is multicast or broadcast.

.RE

.TP

ip neighbour show

list neighbour entries

.RS

.TP

.BI to " ADDRESS " (default)

the prefix selecting the neighbours to list.

.TP

.BI dev " NAME"

only list the neighbours attached to this device.

.TP

.BI vrf " NAME"

only list the neighbours for given VRF.

.TP

.BI proxy

list neighbour proxies.

.TP

.B unused

only list neighbours which are not currently in use.

.TP

.BI nud " STATE"

only list neighbour entries in this state.

.I NUD_STATE

takes values listed below or the special value

.B all

which means all states. This option may occur more than once.

If this option is absent,

.B ip

lists all entries except for

.B none

and

.BR "noarp" .

.RE

.TP

ip neighbour flush

flush neighbour entries

.RS

This command has the same arguments as

.B 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

.B permanent

and

.BR "noarp" .

.PP

With the

.B -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,

.B ip neigh flush

also dumps all the deleted neighbours.

.RE

.SH EXAMPLES

.PP

ip neighbour

.RS

Shows the current neighbour table in kernel.

.RE

.PP

ip neigh flush dev eth0

.RS

Removes entries in the neighbour table on device eth0.

.RE

.SH SEE ALSO

.br

.BR ip (8)

.SH AUTHOR

Original Manpage by Michail Litvak <mci@owl.openwall.com>