Gratuitous Arp; Gratuitous Arp Global Settings - D-Link Xstack DES-3528 Series Reference Manual

xStack® DES-3528/DES-3552 Series Layer 2 Managed Stackable Fast Ethernet Switch Web UI Reference Guide
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Gratuitous ARP

Gratuitous ARP Global Settings

An ARP announcement (also known as Gratuitous ARP) is a packet (usually an ARP Request) containing a valid
SHA and SPA for the host which sent it, with TPA equal to SPA. Such a request is not intended to solicit a reply,
but merely updates the ARP caches of other hosts which receive the packet.
This is commonly done by many operating systems on startup, and helps to resolve problems which would
otherwise occur if, for example, a network card had recently been changed (changing the IP address to MAC
address mapping) and other hosts still had the old mapping in their ARP cache.
The user can enable or disable the gratuitous ARP global settings here.
To view the following window, click Management > Gratuitous ARP > Gratuitous ARP Global Settings, as
shown below:
The fields that can be configured are described below:
Parameter
Send On IP Interface
Status Up
Send On Duplicate IP
Detected
Gratuitous ARP
Learning
Click the Apply button to accept the changes made.
NOTE: With the gratuitous ARP learning, the system will not learn new entry but only do the update on
the ARP table based on the received gratuitous ARP packet.
Figure 3-4 Gratuitous ARP Global Settings Window
Description
The command is used to enable/disable sending of gratuitous ARP request packet while
the IPIF interface become up. This is used to automatically announce the interface's IP
address to other nodes. By default, the state is disabled, and only one gratuitous ARP
packet will be broadcast.
The command is used to enable/disable the sending of gratuitous ARP request packet
while a duplicate IP is detected. By default, the state is disabled. For this command, the
duplicate IP detected means that the system received an ARP request packet that is
sent by an IP address that match the system's own IP address. In this case, the system
knows that somebody out there uses an IP address that is conflict with the system. In
order to reclaim the correct host of this IP address, the system can send out the
gratuitous ARP request packets for this duplicate IP address.
Normally, the system will only learn the ARP reply packet or a normal ARP request
packet that asks for the MAC address that corresponds to the system's IP address. The
command is used to enable/disable learning of ARP entry in ARP cache based on the
received gratuitous ARP packet. The gratuitous ARP packet is sent by a source IP
address that is identical to the IP that the packet is queries for. By default, the state is
Disabled status.
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