Users Guide

given in the payload. Then, all the traffic destined for the cluster is flooded out of all member ports. Because
all the servers in the cluster receive traffic, failover and balancing are preserved.
Enable and Disable VLAN Flooding
• The older ARP entries are overwritten whenever newer NLB entries are learned.
• All ARP entries, learned after you enable VLAN flooding, are deleted when you disable VLAN flooding,
and RP2 triggers an ARP resolution. Disable VLAN flooding with the no ip vlan-flooding command.
• When you add a port to the VLAN, the port automatically receives traffic if you enabled VLAN flooding.
Old ARP entries are not deleted or updated.
• When you delete a member port, its ARP entries are also deleted from the content addressable memory
(CAM).
• Port channels in the VLAN also receive traffic.
• There is no impact on the configuration from saving the configuration.
• If you enable VLAN flooding, it displays in the show running-config command output that displays
the
ip vlan-flooding CLI configuration. This is the only output where you see the VLAN flooding
status (enabled or disabled).
Configuring a Switch for NLB
To enable a switch for Unicast NLB mode, perform the following steps:
• Enter the ip vlan-flooding command to specify that all Layer 3 unicast routed data traffic going
through a VLAN member port floods across all the member ports of that VLAN.
CONFIGURATION mode
ip vlan-flooding
There might be some ARP table entries that are resolved through ARP packets, which had the Ethernet
MAC SA different from the MAC information inside the ARP packet. This unicast data traffic flooding
occurs only for those packets that use these ARP entries.
Enabling a Switch for Multicast NLB
To enable a switch for Multicast NLB mode, perform the following steps:
1 Add a static ARP entry by entering the arp ip-address multicast-mac-address command in
Global configuration mode to associate an IP address with a multicast MAC address in the switch.
CONFIGURATION mode
arp ip-address multicast-mac-address interface
Microsoft Network Load Balancing 559