H3C Technologies H3C S12500 Series Switches - Manual (Page 24)

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{
If the virtual IP address of the VRRP group is associated with a virtual MAC address, the sender
MAC address in the gratuitous ARP packet is the virtual MAC address of the virtual router.
{
If the virtual IP address of the VRRP group is associated with the real MAC address of an
interface, the sender MAC address in the gratuitous ARP packet is the MAC address of the
interface on the master router in the VRRP group.
• Update MAC entries of devices in the VLANs having ambiguous VLAN termination configured.
In VRRP configuration, if ambiguous VLAN termination is configured for many VLANs and VRRP
groups, interfaces configured with VLAN termination need to be disabled from transmitting
broadcast/multicast packets. Also, a VRRP control VLAN needs to be configured so that VRRP
advertisements can be transmitted within the control VLAN only. In such cases, you can enable
periodic sending of gratuitous ARP packets containing the VRRP virtual IP address, and the primary
IP address or a manually configured secondary IP address of the sending interface on the
subinterfaces. In this way, when a VRRP failover occurs, devices in the VLANs having ambiguous
VLAN termination configured can use the gratuitous ARP packets to update their corresponding
MAC entries in time.
33B
Configuration procedure
The following conditions apply to the gratuitous ARP configuration:
• You can enable periodic sending of gratuitous ARP packets on up to 1024 interfaces.
• Periodic sending of gratuitous ARP packets takes effect only when the link of the enabled interface
goes up and an IP address has been assigned to the interface.
• If you change the interval for sending gratuitous ARP packets, the configuration is effective at the
next sending interval.
• The frequency of sending gratuitous ARP packets may be much lower than the sending interval set
by the user in any of the following circumstances:
{
This function is enabled on multiple interfaces.
{
Each interface is configured with multiple secondary IP addresses.
{
A small sending interval is configured when the previous two conditions exist.
To configure gratuitous ARP:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable learning of gratuitous
ARP packets.
gratuitous-arp-learning enable
By default, learning of gratuitous
ARP packets is enabled.
3. Enable the device to send
gratuitous ARP packets upon
receiving ARP requests whose
sender IP address belongs to
a different subnet.
gratuitous-arp-sending enable
By default, a device does not send
gratuitous ARP packets upon
receiving ARP requests whose
sender IP address belongs to a
different subnet.
4. Enter interface view.
interface interface-type
interface-number
N/A
5. Enable periodic sending of
gratuitous ARP packets and
set the sending interval.
arp send-gratuitous-arp [ interval
milliseconds ] By default, periodic sending of
gratuitous ARP packets is disabled.