Network Load Balancing

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Applies to: Windows Server 2022, Windows Server 2019, Windows Server 2016

In this topic, we provide you with an overview of the Network Load Balancing (NLB) feature in Windows Server 2016. You can use NLB to manage two or more than servers as a single virtual cluster. NLB enhances the availability and scalability of Internet server applications such as those used on spider web, FTP, firewall, proxy, virtual private network (VPN), and other mission-disquisitional servers.

Annotation

Windows Server 2016 includes a new Azure-inspired Software Load Balancer (SLB) as a component of the Software Defined Networking (SDN) infrastructure. Use SLB instead of NLB if you lot are using SDN, are using non-Windows workloads, need outbound network accost translation (NAT), or need Layer 3 (L3) or non-TCP based load balancing. Yous can continue to use NLB with Windows Server 2016 for non-SDN deployments. For more than data about SLB, meet Software Load Balancing (SLB) for SDN.

The Network Load Balancing (NLB) characteristic distributes traffic across several servers by using the TCP/IP networking protocol. By combining two or more computers that are running applications into a single virtual cluster, NLB provides reliability and operation for web servers and other mission-critical servers.

The servers in an NLB cluster are chosen hosts, and each host runs a separate re-create of the server applications. NLB distributes incoming client requests beyond the hosts in the cluster. Y'all can configure the load that is to be handled by each host. You lot can also add hosts dynamically to the cluster to handle increased load. NLB tin can also direct all traffic to a designated single host, which is called the default host.

NLB allows all of the computers in the cluster to be addressed past the same set of IP addresses, and it maintains a set of unique, defended IP addresses for each host. For load-balanced applications, when a host fails or goes offline, the load is automatically redistributed among the computers that are however operating. When information technology is ready, the offline computer can transparently rejoin the cluster and regain its share of the workload, which allows the other computers in the cluster to handle less traffic.

Practical applications

NLB is useful for ensuring that stateless applications, such equally web servers running Internet Data Services (IIS), are bachelor with minimal downtime, and that they are scalable (by calculation boosted servers as the load increases). The following sections describe how NLB supports loftier availability, scalability, and manageability of the amassed servers that run these applications.

High availability

A high availability system reliably provides an adequate level of service with minimal reanimation. To provide high availability, NLB includes congenital-in features that can automatically:

  • Detect a cluster host that fails or goes offline, and and so recover.

  • Balance the network load when hosts are added or removed.

  • Recover and redistribute the workload within ten seconds.

Scalability

Scalability is the measure of how well a figurer, service, or awarding can grow to meet increasing performance demands. For NLB clusters, scalability is the ability to incrementally add one or more systems to an existing cluster when the overall load of the cluster exceeds its capabilities. To support scalability, you can do the post-obit with NLB:

  • Residual load requests beyond the NLB cluster for individual TCP/IP services.

  • Support up to 32 computers in a single cluster.

  • Balance multiple server load requests (from the aforementioned client or from several clients) across multiple hosts in the cluster.

  • Add hosts to the NLB cluster as the load increases, without causing the cluster to fail.

  • Remove hosts from the cluster when the load decreases.

  • Enable loftier performance and low overhead through a fully pipelined implementation. Pipelining allows requests to be sent to the NLB cluster without waiting for a response to a previous request.

Manageability

To support manageability, you tin exercise the following with NLB:

  • Manage and configure multiple NLB clusters and the cluster hosts from a single computer past using NLB Manager or the Network Load Balancing (NLB) Cmdlets in Windows PowerShell.

  • Specify the load balancing behavior for a unmarried IP port or group of ports past using port management rules.

  • Ascertain unlike port rules for each website. If y'all use the aforementioned gear up of load-counterbalanced servers for multiple applications or websites, port rules are based on the destination virtual IP address (using virtual clusters).

  • Directly all client requests to a single host past using optional, unmarried-host rules. NLB routes client requests to a particular host that is running specific applications.

  • Block undesired network admission to certain IP ports.

  • Enable Internet Grouping Direction Protocol (IGMP) support on the cluster hosts to control switch port flooding (where incoming network packets are sent to all ports on the switch) when operating in multicast mode.

  • Get-go, end, and control NLB actions remotely by using Windows PowerShell commands or scripts.

  • View the Windows Event Log to bank check NLB events. NLB logs all actions and cluster changes in the event log.

Important functionality

NLB is installed as a standard Windows Server networking driver component. Its operations are transparent to the TCP/IP networking stack. The following figure shows the relationship between NLB and other software components in a typical configuration.

Network Load Balancing and other software components

Post-obit are the primary features of NLB.

  • Requires no hardware changes to run.

  • Provides Network Load Balancing Tools to configure and manage multiple clusters and all of the hosts from a unmarried remote or local reckoner.

  • Enables clients to admission the cluster past using a single, logical Internet name and virtual IP address, which is known every bit the cluster IP address (it retains individual names for each figurer). NLB allows multiple virtual IP addresses for multihomed servers.

Annotation

When you deploy VMs equally virtual clusters, NLB does non require servers to be multihomed to have multiple virtual IP addresses.

  • Enables NLB to be spring to multiple network adapters, which enables you to configure multiple contained clusters on each host. Support for multiple network adapters differs from virtual clusters in that virtual clusters let yous to configure multiple clusters on a single network adapter.

  • Requires no modifications to server applications so that they can run in an NLB cluster.

  • Can be configured to automatically add a host to the cluster if that cluster host fails and is after brought dorsum online. The added host can first handling new server requests from clients.

  • Enables you to take computers offline for preventive maintenance without agonizing the cluster operations on the other hosts.

Hardware requirements

Following are the hardware requirements to run an NLB cluster.

  • All hosts in the cluster must reside on the aforementioned subnet.

  • There is no restriction on the number of network adapters on each host, and different hosts tin can have a different number of adapters.

  • Inside each cluster, all network adapters must be either multicast or unicast. NLB does non support a mixed environment of multicast and unicast within a unmarried cluster.

  • If you use the unicast manner, the network adapter that is used to handle client-to-cluster traffic must support irresolute its media admission control (MAC) accost.

Software requirements

Following are the software requirements to run an NLB cluster.

  • Simply TCP/IP tin be used on the adapter for which NLB is enabled on each host. Do not add whatsoever other protocols (for example, IPX) to this adapter.

  • The IP addresses of the servers in the cluster must be static.

Annotation

NLB does not back up Dynamic Host Configuration Protocol (DHCP). NLB disables DHCP on each interface that it configures.

Installation information

You can install NLB by using either Server Director or the Windows PowerShell commands for NLB.

Optionally you tin can install the Network Load Balancing Tools to manage a local or remote NLB cluster. The tools include Network Load Balancing Manager and the NLB Windows PowerShell commands.

Installation with Server Manager

In Server Director, you can use the Add Roles and Features Wizard to add the Network Load Balancing feature. When you complete the wizard, NLB is installed, and you do not demand to restart the reckoner.

Installation with Windows PowerShell

To install NLB past using Windows PowerShell, run the following control at an elevated Windows PowerShell prompt on the figurer where you want to install NLB.

              Install-WindowsFeature NLB -IncludeManagementTools

Afterwards installation is consummate, no restart of the computer is required.

For more information, see Install-WindowsFeature.

Network Load Balancing Manager

To open Network Load Balancing Manager in Server Manager, click Tools, and then click Network Load Balancing Director.

Additional resources

The following table provides links to additional data most the NLB feature.

Content type References
Deployment Network Load Balancing Deployment Guide | Configuring Network Load Balancing with Terminal Services
Operations Managing Network Load Balancing Clusters | Setting Network Load Balancing Parameters | Controlling Hosts on Network Load Balancing Clusters
Troubleshooting Troubleshooting Network Load Balancing Clusters | NLB Cluster Events and Errors
Tools and settings Network Load Balancing Windows PowerShell cmdlets
Community resources Loftier Availability (Clustering) Forum