All servers in an NLB cluster use the same cluster IP address and cluster MAC address. An NLB cluster can work in unicast or multicast mode where the cluster MAC address is a unicast or multicast MAC address accordingly. When a device is directly connected to NLB servers and functions as their access gateway, the device sends a packet from clients to the cluster IP address, where it is forwarded to every server in the NLB cluster. The servers themselves determine whether to process the packet. If a device does not support multi-interface ARP, physical link loopback can be used to enable the device to send the packet destined for the cluster IP address to each server in an NLB cluster.
The networking for physical link loopback varies depending on the switch system (a single switch, stack system or VRRP group). For details, see Interworking with an NLB Cluster. The configurations include disabling STP, RSTP, VBST, or MSTP, and configuring a static ARP entry (only when an NLB cluster works in multicast mode).
Run system-view
The system view is displayed.
Run interface interface-type interface-number
The interface view is displayed.
Run undo stp enable or stp disable
STP, RSTP, VBST, or MSTP is disabled.
By default, STP, RSTP, VBST, or MSTP is enabled on devices.
Run quit
Return to the system view.
Run system-view
The system view is displayed.
Run arp static ip-address mac-address vid vlan-id interface interface-type interface-number
The static ARP entry is configured.
In the static ARP entry, the IP address is the cluster IP address, the MAC address is the cluster multicast MAC address, and the outbound interface is the interface where the VLAN to which the NLB cluster's gateway belongs is configured.