NLB Host

Applies To: Windows Server 2008

Each Network Load Balancing (NLB) host runs a separate copy of the desired server applications (such as applications for Web, FTP, and Telnet servers). NLB distributes incoming client requests across the hosts in the cluster. The load weight to be handled by each host can be configured as necessary. You can also add hosts dynamically to the cluster to handle increased load. In addition, NLB can direct all traffic to a designated single host, which is called the default host.

Managed Entities

The following is a list of the managed entities that are included in this managed entity:

Name Description

Network Adapter

The network adapter handles the network traffic for Network Load Balancing (NLB) cluster operations (the traffic for all hosts in the cluster).



The following is a list of all aspects that are part of this managed entity:

Name Description

NLB Bi-Directional Affinity (BDA) Configuration

Bi-directional affinity creates multiple instances of Network Load Balancing (NLB) on the same host, which work in tandem to ensure that responses from published servers are routed through the appropriate ISA servers in a cluster. Bi-directional affinity is commonly used when NLB is configured with Internet Security and Acceleration (ISA) servers. If bi-directional affinity is not consistent across all NLB hosts or if NLB fails to initialize bi-directional affinity, the NLB cluster will remain in the converging state until a consistent teaming configuration is detected.


NLB Cluster Control

The Network Load Balancing (NLB) cluster operates normally when all NLB components are compatible. If some components are incompatible, then you may run into issues managing and controlling the cluster.



NLB Connection Tracking and Load Balancing

The Network Load Balancing (NLB) driver on the host tracks connections to maintain client/network affinity configured on the NLB cluster. If the driver is not functioning properly, NLB may not be able to track TCP connections or may experience load distribution errors.


NLB Dedicated IP (DIP) Addresses Functionality

The dedicated IP addresses in Network Load Balancing (NLB) must be properly configured and be able to contact individual NLB cluster hosts. If the dedicated IP address is not configured correctly, you cannot use it to manage the host or for other non-cluster-related communication.


NLB Denial-of-service Protection

Network Load Balancing (NLB) Denial-of-service Protection protects an NLB cluster from denial-of-service attacks such as SYN attacks and timer starvation. If protection is not present, the NLB cluster may not perform optimally and the connections in the cluster may fail.

NLB Filter Hooks Configuration

Filter hooks help to direct traffic in a Network Load Balancing (NLB) cluster by filtering network packets. If the filter hooks are not properly configured, the NLB cluster will continue to converge and operate normally, however, the server application that is running with NLB will not be able to properly register the hooks.

NLB General Functionality

General Functionality provides information about whether the hosts are functioning properly, such as when a new host has started load balancing traffic, when an inactive host has suspended cluster operations, and when NLB cluster is initiating convergence because a new host is joining the cluster.

NLB Host Configuration

Hosts in a Network Load Balancing (NLB) cluster are configured to load balance network traffic. Host configuration is set by using NLB Manager, and if it is not configured properly, the NLB cluster may not function correctly.


NLB Host State Persistence

When configured to do so, the Network Load Balancing (NLB) host state will persist whenever the NLB cluster shuts down and restarts.


NLB Port Rules Configuration

In a Network Load Balancing (NLB) cluster, port rules are configured to control how each port's cluster network traffic is handled. The NLB cluster may fail to converge unless each port rule has a unique host priority (a number between 1 and 32), the port rules are consistent on all cluster hosts, you are using the proper number of port rules, and the virtual IP address is specified in a valid IPv4 or IPv6 address format.


NLB Cluster