# ip-neighbour

## 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.
    


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