# ARP

The `nv unset` commands remove the configuration you set with the equivalent `nv set` commands. This guide only describes an `nv unset` command if it differs from the `nv set` command.

## nv set interface <interface-id> neighbor ipv4 <ip-address> lladdr <lladdr-id>

Configures a static ARP table entry for an interface with an IPv4 address associated with a MAC address for easy management or as a security measure to prevent spoofing and other nefarious activities.

### Command Syntax

Syntax | Description
--- | ---
`<interface-id>` | The interface you want to configure.
`<ip-address>` | The static IP address.
`<lladdr-id>` | The MAC address you want to associate with IPv4 address.

### Version History

Introduced in Cumulus Linux 5.7.0

### Example

    cumulus@switch:~$ nv set interface swp51 neighbor ipv4 10.5.5.51 lladdr 00:00:5E:00:53:51

## nv set interface <interface-id> neighbor ipv4 <ip-address> lladdr <lladdr-id> flag

Configures a flag to indicate that the neighbor in the ARP table entry is a router (`is-router`) or learned externally (`ext_learn`)

### Command Syntax

Syntax | Description
--- | ---
`<interface-id>` | The interface you want to configure.
`<ip-address>` | The static IP address.
`<lladdr-id>` | The MAC address you want to associate with IPv4 address.

### Version History

Introduced in Cumulus Linux 5.7.0

### Example

    cumulus@switch:~$ nv set interface swp51 neighbor ipv4 10.5.5.51 lladdr 00:00:5E:00:53:51 flag is-router

## nv set interface <interface-id> neighbor ipv4 <ip-address> lladdr <lladdr-id> state

Configures the state of the neighbor in the ARP table entry (`delay`, `failed`, `incomplete`, `noarp`, `permanent`, `probe`, `reachable`, or `stale`).

### Command Syntax

Syntax | Description
--- | ---
`<interface-id>` | The interface you want to configure.
`<ip-address>` | The static IP address.
`<lladdr-id>` | The MAC address you want to associate with IPv4 address.

### Version History

Introduced in Cumulus Linux 5.7.0

### Example

    cumulus@switch:~$ nv set interface swp51 neighbor ipv4 10.5.5.51 lladdr 00:00:5E:00:53:51 state permanent

## nv set system global arp base-reachable-time

Configures how long a neighbor cache entry is valid. The entry is valid for at least the value between the base reachable time divided by two and three times the base reachable time divided by two. You can specify a value between 30 and 2147483 seconds. The default value is auto; NVUE derives the value for auto from the `/etc/sysctl.d/neigh.conf` file.

### Version History

Introduced in Cumulus Linux 5.6.0

### Example

    cumulus@switch:~$ nv set system global arp base-reachable-time 50