D-Link DGS-3612G Product Manual - Page 204

xStack® DGS-3600 Series Layer 3 Managed Gigabit Ethernet Switch Gratuitous ARP 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 To open the Gratuitous ARP Settings window, click L3 Features > Gratuitous ARP Settings, as shown below: Figure 4- 21. Gratuitous ARP Settings window Once you have made the desired gratuitous ARP setting changes, click Apply. To modify a current entry, click the corresponding Modify button of the entry, which will reveal the following window to be configured: Figure 4- 22. Gratuitous ARP Table - Edit window The following fields can be set or viewed: Parameter Description Send on IPIF status This is used to enable/disable the sending of gratuitous ARP request packets while an IPIF up interface comes up. This is used to automatically announce the interface's IP address to other nodes. By default, the state is Disabled, and only one ARP packet will be broadcast. Send on Duplicate_IP_Detected This is used to enable/disable the sending of gratuitous ARP request packets while a duplicate IP is detected. By default, the state is Disabled. Duplicate IP detected means that the system received an ARP request packet that is sent by an IP address that matches the system's own IP address. Gratuitous ARP Learning This is used to enable/disable updating ARP cache based on the received gratuitous ARP packet. If a switch receives a gratuitous ARP packet, it should add or update the ARP entry. This is Disabled by default. Gratuitous ARP Trap & Log The switch can trap and log IP conflict events to inform the administrator. By default, trap is Disabled and event log is also disabled. Gratuitous ARP Periodical Send Interval This is used to configure the interval for the periodical sending of gratuitous ARP request packets. By default, the interval is 0. After making the desired changes, click Apply to implement the new Gratuitous ARP Table entry. 188