H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – ARP
H3C S7500E Series Ethernet Switches Chapter 1 ARP Configuration
1-7
[Sysname-vlan-interface10] quit
[Sysname] arp static 192.168.1.1 000f-e201-0000 10 gigabitethernet2/0/10
1.3 Configuring Gratuitous ARP
1.3.1 Introduction to Gratuitous ARP
A gratuitous ARP packet is a special ARP packet, in which the source IP address and
destination IP address are both the IP address of the sender, the source MAC address
is the MAC address of the sender, and the destination MAC address is a broadcast
address.
A device can implement the following functions by sending gratuitous ARP packets:
z Determining whether its IP address is already used by another device.
z Informing other devices of its MAC address change so that they can update their
ARP entries.
A device receiving a gratuitous ARP packet can add the information carried in the
packet to its own dynamic ARP mapping table if it finds no corresponding ARP entry for
the ARP packet in the cache.
1.3.2 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
Required
Enabled by default.
1.4 Configuring ARP Source Suppression
1.4.1 Introduction to ARP Source Suppression
If a host attacks the device on a network by sending large amounts of IP packets whose
IP addresses cannot be resolved: