Chapter 46 ARP Setup
GS3700/XGS3700 Series User’s Guide
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ICMP reply from host B, it sends out an ARP request to get host A’s MAC address and updates the
ARP table with host A’s ARP reply. The Switch then can forward host B’s ICMP reply to host A.
46.1.2.2 Gratuitous-ARP
A gratuitous ARP is an ARP request in which both the source and destination IP address fields are
set to the IP address of the device that sends this request and the destination MAC address field is
set to the broadcast address. There will be no reply to a gratuitous ARP request.
A device may send a gratuitous ARP packet to detect IP collisions. If a device restarts or its MAC
address is changed, it can also use gratuitous ARP to inform other devices in the same network to
update their ARP table with the new mapping information.
In Gratuitous-ARP learning mode, the Switch updates its ARP table with either an ARP reply or a
gratuitous ARP request.
46.1.2.3 ARP-Request
When the Switch is in ARP-Request learning mode, it updates the ARP table with both ARP replies,
gratuitous ARP requests and ARP requests.
A
B
ARP Request
ARP Reply
I CMP Request
ARP Request
ARP Reply
I CMP Request
I CMP Reply
ARP Request
ARP Reply
I CMP Reply
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