H3C Technologies H3C WX3000 Series Unified Switches - Manual (Page 400)

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the manually configured IP binding table, refer to DHCP snooping section in DHCP in H3C WX3000
Series Unified Switches Switching Engine Configuration Guide.
After you enable the ARP attack detection function, the device will check the following items of an ARP
packet: the source MAC address, source IP address, port number of the port receiving the ARP packet,
and the ID of the VLAN the port resides. If these items match the entries of the DHCP snooping table or
the manual configured IP binding table, the device will forward the ARP packet; if not, the device
discards the ARP packet.
z
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.
z
With the ARP restricted forwarding function enabled, ARP request packets are forwarded through
trusted ports only; ARP response packets 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:
z
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.
z
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:
z
Determine whether or not IP address conflicts exist between it and other network devices.
z
Trigger other network devices to update its hardware address stored in their caches.
The gratuitous ARP packet learning function:
When the gratuitous ARP packet learning function is enabled on a device and the device receives a
gratuitous ARP packet, the device updates the existing ARP entry (contained in the cache of the device)
that matches the received gratuitous ARP packet using the hardware address of the sender carried in
the gratuitous ARP packet.
Configuring ARP
Configuring ARP Basic Functions
Follow these steps to configure ARP basic functions:
To do… Use the command… Remarks
Enter system view system-view —
Add a static ARP entry
arp static ip-address mac-address
[ vlan-id interface-type
interface-number
]
Optional
By default, the ARP mapping table is
empty, and the address mapping entries
are created dynamically by ARP.
Configure the ARP aging
timer
arp timer aging aging-time
Optional
By default, the ARP aging timer is set to
20 minutes.