Introduction To Gratuitous Arp - 3Com 5500-SI Configuration Manual

Introduction to
Gratuitous ARP
Note that:
Static ARP map entry will be always valid as long as the Switch works normally. But
■
if the VLAN corresponding to the ARP mapping entry is deleted, the ARP mapping
entry will be also deleted. The valid period of dynamic ARP map entries will last
only 20 minutes by default.
The parameter
■ vlan-id
user, and the Ethernet port specified behind this parameter must belong to the
VLAN.
The aggregation port or port with LACP enabled cannot be set as the egress port
■
of static ARP.
Configuring the Dynamic ARP Aging Timer
For purpose of flexible configuration, the system provides the following commands to
assign dynamic ARP aging period. When the system learns a dynamic ARP entry, its
aging period is based on the current value configured.
Perform the following configuration in System View.
Table 270 Configuring the Dynamic ARP Aging Timer
Operation
Configure the dynamic ARP aging timer
Restore the default dynamic ARP aging time
By default, the aging time of the dynamic ARP aging timer is 20 minutes.
Configuring the Creation of ARP Entries for Multicast Packets
Use the following command to specify whether the Switch should create ARP table
entries for multicast MAC addresses. Address resolution, for multicast packets, is not
required because the IANA (Internet Assigned Numbers Authority) have reserved a
block of Ethernet addresses that map on to the Class D multicast addresses.
Perform the following configuration in System View.
Table 271 Configuring the Creation of ARP Entries for Multicast Packets
Operation
Configure the Switch NOT to create ARP entries
Configure the Switch to create ARP entries
By default, this feature is enabled.
The following are the characteristics of gratuitous ARP packets:
Both source and destination IP addresses carried in a gratuitous ARP packet are the
■
local IP address, and the source MAC address carried in the packet is the local
MAC address.
If a device finds that the IP address carried in a received gratuitous packet conflict
■
with that of its own, it returns an ARP response to the sending device to notify of
the IP address conflict.
must be the ID of a VLAN that has been created by the
Command
arp timer aging aging_time
undo arp timer aging

Introduction to Gratuitous ARP 275

Command
arp check enable
undo arp check enable