H3C Technologies H3C S7500E Series Switches - Manual (Page 20)

1-8
A device implements the following functions by sending gratuitous ARP packets:
z Determining whether its IP address is already used by another device. If the IP address is already
used, the device issuing the gratuitous ARP packet will be informed by an ARP reply of the
conflict.
z Informing other devices about the change of its MAC address so that they can update their ARP
entries.
Enabling Learning of Gratuitous ARP Packets
With this feature enabled, a device receiving a gratuitous ARP packet adds the sender IP and MAC
addresses carried in the packet to its ARP table if no corresponding ARP entry exists. If a
corresponding ARP entry is found, the device updates the ARP entry.
After this feature is disabled, the device will use the address information in the received gratuitous ARP
packets to update the existing ARP entries only, but not to create new ARP entries.
Configuring Gratuitous ARP
Follow these steps to configure gratuitous ARP:
To do… Use the command… Remarks
Enter system view system-view —
Enable the device to send
gratuitous ARP packets when
receiving ARP requests from
another network segment
gratuitous-arp-sending enable
Required
By default, a device cannot send
gratuitous ARP packets when
receiving ARP requests from
another network segment.
Enable the gratuitous ARP packet
learning function
gratuitous-arp-learning enable
Optional
Enabled by default.
Displaying and Maintaining ARP
To do… Use the command… Remarks
Display ARP entries in the ARP
table (for distributed devices)
display arp [ [ all | dynamic | static ] [ slot slot-number ] |
vlan vlan-id | interface interface-type interface-number ]
[ [ verbose ] [ | { begin | exclude | include }
regular-expression ] | count ]
Available in
any view
Display ARP entries in the ARP
table (for distributed IRF
devices)
display arp [ [ all | dynamic | static ] [ chassis
chassis-number slot slot-number ] | vlan vlan-id | interface
interface-type interface-number ] [ [ verbose ] [ | { begin |
exclude | include } regular-expression ] | count ]
Available in
any view