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 ] [ 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 }

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 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.

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.

SEE ALSO
ip(8)

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