arp

• Command Function
• Syntax
• Parameter Description
• Usage
• Example

Command Function

On an Ethernet, hosts communicate with each other using MAC addresses (non-IP addresses). Therefore, IP addresses must be converted into MAC addresses so that hosts can communicate with each other on a LAN (Ethernet). To resolve this issue, the host stores a table containing the mapping between IP addresses and MAC addresses, that is, the ARP cache table. When the host needs to send an IP packet to the destination IP address on a LAN, the host can query the destination MAC address from the ARP cache table. The ARP cache table is maintained by the TCP/IP protocol stack. You can run the arp command to view and modify the ARP cache table.

Syntax

arp

arp [-i IF] -s IPADDR HWADDR

arp [-i IF] -d IPADDR

Parameter Description

Table 1 Parameters

Usage

• The arp command is used to query and modify the ARP cache table of the TCP/IP protocol stack. If ARP entries for IP addresses on different subnets are added, the protocol stack returns a failure message.
• This command can be used only after the TCP/IP protocol stack is enabled.

Example

Example:

1. Enter arp.

   Figure 1 Printing the entire ARP cache table

   

   Table 2 Output description

   Parameter	Description
   Address	Indicates the IPv4 address of a network device.
   HWaddress	Indicates the MAC address of a network device.
   Iface	Indicates the name of the interface used by the ARP entry.
   Type	Indicates whether the ARP entry is dynamic or static. A dynamic ARP entry is automatically created by the protocol stack, and a static ARP entry is added by the user.