D-Link DI-1750 Reference Manual page 152

The select the specified type and number.
The specified interface in upward commands must be an other interface holding IP address of the
router, but not also an unnumbered interface. And this interface should be also enabled (In showing of
command show interface the interface is "up").
An example of how to configure serial interfaces can be found in the "Serial Interface Configuration
Example" section at the end of the chapter.
6.2.2 Configure Address Resolution
The IP implementation allows you to control IP address resolution and some other functions. The
following sections describe how to configure address resolution:
♦ Establish Address Resolution
♦ Map Host Names to IP Addresses
1. Establish Address Resolution
An IP device can have both a local address, which uniquely identifies the device on its local segment or
LAN, and a network address, which identifies the network the device belongs to. The local address is
more properly known as a data link address because it is contained in the data link layer part of the
packet header and is read by data link devices. The more technically inclined will refer to local
addresses as MAC addresses, because the Media Access Control (MAC) sublayer within the data link
layer processes addresses for the layer.
To communicate with a device on Ethernet, for example, the router first must determine the 48-bit MAC
or local data link address of that device. The process of determining the local data link address from an
IP address is called address resolution. The process of determining the IP address from a local data
link address is called reverse address resolution.
The router uses two forms of address resolution: Address Resolution Protocol (ARP) and proxy ARP.
The ARP and proxy ARP protocols are respectively defined in RFC 826 and RFC 1027.
The Address Resolution Protocol (ARP) is used to associate IP addresses with media or MAC
addresses. Taking an IP address as input, ARP determines the associated media address. Once a
media or MAC address is determined, the IP address/media address association is stored in an ARP
cache for rapid retrieval. Then the IP datagram is encapsulated in a link-layer frame and sent over the
network.
Perform the following tasks to set address resolution on the router:
♦ Define a Static ARP Cache
♦ Enable Proxy ARP
Define a Static ARP Cache
ARP and other address resolution protocols provide a dynamic mapping between IP addresses and
media addresses. Because most hosts support dynamic address resolution, you generally do not need
to specify static ARP cache entries. If you do need to define them, you can do so globally. Doing this
task installs a permanent entry in the ARP cache. The router uses this entry to translate 32-bit IP
addresses into 48-bit hardware addresses. In addition, you can also specify the router to reply to ARP
requests instead of other hosts.
Maybe you do not wish the ARP table live permanently, here you can configure the live time of ARP
table. The following two tables list the tasks to provide static mapping between IP addresses and media
address.
arp ip-address hardware-address
arp ip-address hardware-address
set-alias
Command
Model Name
Purpose
Globally associate an IP address with a media (hardware)
address in the ARP cache.
Specify that the router respond to ARP requests as if it were
the owner of the specified IP address.
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