Introduction To Gratuitous Arp; Configuring Arp; Configuring Arp Basic Functions - H3C S5100-SI Operation Manual

the manual configured IP binding table, the switch will forward the ARP packet; if not, the switch
discards the ARP packet.
With trusted ports configured, ARP packets coming from the trusted ports will not be checked,
while those from other ports will be checked through the DHCP snooping table or the manually
configured IP binding table.
With the ARP restricted forwarding function enabled, ARP request packets coming from untrusted
port are forwarded through trusted ports only; ARP response packets coming from untrusted port
are forwarded according to the MAC addresses in the packets, or through trusted ports if the MAC
address table contains no such destination MAC addresses.

Introduction to Gratuitous ARP

The following are the characteristics of gratuitous ARP packets:
Both source and destination IP addresses carried in a gratuitous ARP packet are the local
addresses, and the source MAC address carried in it is the local MAC addresses.
If a device finds that the IP addresses carried in a received gratuitous packet conflict with those of
its own, it returns an ARP response to the sending device to notify of the IP address conflict.
By sending gratuitous ARP packets, a network device can:
Determine whether or not IP address conflicts exist between it and other network devices.
Trigger other network devices to update its hardware address stored in their caches.
With the gratuitous ARP packet learning function enabled:
A device receiving a gratuitous ARP packet adds the information carried in the packet to its own
dynamic ARP table if it finds no corresponding ARP entry for the ARP packet exists in the cache.

Configuring ARP

Configuring ARP Basic Functions

Follow these steps to configure ARP basic functions:
To do...
Enter system view
Add a static ARP entry
Configure the ARP aging timer
Enable the ARP entry checking
function (that is, disable the
switch from learning ARP
entries with multicast MAC
addresses)
Use the command...
system-view
arp static ip-address
mac-address [ vlan-id
interface-type
interface-number ]
arp timer aging aging-time
arp check enable
1-5
Remarks
—
Optional
By default, the ARP mapping
table is empty, and entries are
created dynamically by ARP.
Optional
20 minutes by default.
Optional
Enabled by default.