R21xx-HP FlexFabric 11900 Layer 3 IP Services Configuration Guide

Configuring multicast ARP

Microsoft Network Load Balancing (NLB) is a load balancing technology for server clustering developed

on Windows Server. In a medium or small data center that uses the Windows Server operating system,

the proper cooperation of the switch and NLB is very important. The switch series supports cooperation

with NLB by multicast ARP. For more information about NLB, see the related documents of Windows

Sever.

NLB supports load sharing and redundancy among servers within a cluster. To implement fast failover,

NLB requires that the switch forwards network traffic to all servers or specified servers in the cluster, and

each server filters out unexpected traffic.

Microsoft NLB provides the following packet sending modes to make the switch forward network traffic

to all servers or specified servers:

• Unicast mode—NLB assigns each cluster member a common MAC address, which is the cluster

MAC address, and changes the source MAC address of each sent packet. Thus, the switch cannot

add the cluster MAC address to its MAC table. In addition, because the cluster MAC address is

unknown to the switch, packets destined to it are forwarded on all the ports of the switch.

• Multicast mode—NLB uses a multicast MAC address that is a virtual MAC address for network

communication (for example 0300-5e11-1111).

• IGMP multicast mode—The switch sends packets only out of the ports that connect to the cluster

members rather than all ports.

IMPORTANT:

Multicast ARP is applicable to only multicast-mode NLB.

To configure multicast ARP:

Ste

Command

Remarks

1. Enter system view.

system-view N/A

2. Disable the ARP entry check

function.

undo arp check enable

N/A

3. Configure a static multicast MAC

address entry.

mac-address multicast mac-address

interface interface-list vlan vlan-id

See IP Multicast Command

Reference.

Displaying and maintaining ARP

IMPORTANT:

Clearing ARP entries from the ARP table might cause communication failures. Make sure the entries to be

cleared do not affect current communications.

Execute display commands in any view and reset commands in user view.