Address Resolution Protocol (Arp); Arp Table; Registering Arp Table - SMC Networks 7824M/VSW - annexe 1 Manual

Management Guide
TigerAccess™ EE
7.12
7.12.1
7.12.1.1
SMC7824M/VSW

Address Resolution Protocol (ARP)

Devices connected to IP network have two addresses, LAN address and network address.
LAN address is sometimes called as a data link address because it is used in Layer 2
level, but more commonly the address is known as a MAC address. A switch on Ethernet
needs a 48-bit-MAC address to transmit packets. In this case, the process of finding a
proper MAC address from the IP address is called an address resolution.
On the other hand, the progress of finding the proper IP address from the MAC address is
called reverse address resolution. The switches and DSLAMs find their MAC addresses
from the IP addresses through address resolution protocol (ARP). ARP saves these ad-
dresses in ARP table for quick search. Referring to the IP addresses in ARP table, the
packets containing the IP address are transmitted to network. When configuring the ARP
table, it is possible to do it only in some specific interfaces.
This chapter consists of the following sections:

ARP Table

•
ARP Alias
•
ARP Inspection
•
Gratuitous ARP
•
Proxy-ARP
•
ARP Table
Hosts typically have an ARP table, which is a cache of IP/MAC address mappings. The
ARP Table automatically maps the IP address to the MAC address of a switch. In addition
to address information, the table shows the age of the entry in the table, the encapsula-
tion method, and the switch interface (VLAN ID) where packets are forwarded.
The switch saves IP/MAC addresses mappings in ARP table for quick search. Referring
to the information in ARP table, packets attached IP address is transmitted to network.
When configuring ARP table, it is possible to do it only in some specific interfaces.

Registering ARP Table

The content of ARP table is automatically registered when the relation between MAC ad-
dress and IP address has been found. The network administrator could use MAC address
of specific IP address in Network by registering on ARP table.
To make specific IP address to be accorded with MAC address, use the following com-
mand.
Command
arp A.B.C.D MACADDR
arp A.B.C.D MACADDR INTER-
FACE
Mode
Sets a static ARP entry, enter the IP address and the
MAC address.
MACADDR: MAC address.
Global
Sets a static ARP entry, enter the IP address, the MAC
address and enter an interface name.
INTERFACE: interface name.
MACADDR: MAC address.
Description
CLI
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