Understanding the concept
In simple
words I must say the network load balancing(NLB) technology distributes traffic across TCP/IP
network. Hence using NLB increases availability, scalability, and
load-balancing performance of your applications on network. Each 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.
When we configure NLB between two servers we have two static IP address those
servers and a commonly shared IP address assigned as cluster IP. The machines all run an algorithm that
determines whose turn is next at responding to requests. They also exchange heartbeats with one
another, so they all know if one server goes down then it won’t allocate any
more requests to him(By default, when a host fails to send heartbeat messages
within five seconds, it has failed) and you can have up to 32 machines in a
cluster.
For more
information refer the below links,
Configuring NLB cluster
Note :NLB does not support Dynamic Host
Configuration Protocol (DHCP). NLB disables DHCP on each interface that it
configures, so the IP addresses must be static. We must have another static IP
address which should be assigned as cluster IP. So make sure that you have it
before this process.
1. You
must install the feature NLB on all servers which and all need to be take part
in NLB clustering. In order to achieve that, From Server manager select Features->Add features and select Network load balancing, Click Next
to continue.
2. Click
on install button and close the installation results window once it succeeds.
3. To
configure the cluster open NLB window. Start->Administrative tools->Network load balancing manager.
4. Now
you need to create the cluster and its hosts which will handle the traffic.
Right-click Network Load Balancing Clusters->Select
New Cluster or Cluster->New to start.
5. In the Host
text box type the name or IP address of the host that is going to be the member
of your NLB(If you are adding the server which is a remote host, make sure that
the feature NLB is installed on that server as well, follow the above steps to
achieve this), and then click Connect.
You may
fail to connect to another server if the NLB feature is not installed on
another server. Select the interface you wish to use for cluster and click Next.
6. In Host
Parameters, select a value in Priority which will be Unique for each host . The host with the
lowest numerical priority among the current members of the cluster handles all
of the cluster's network traffic that is not covered by a port rule. You can
override these priorities or provide load balancing for specific ranges of
ports by specifying rules on the Port rules defines on step 9.
Also you
can add a dedicated IP address if required by clicking Edit button, Click Next.
7. In
Cluster IP Addresses, click Add and type
the cluster IP address that is shared by every host in the cluster. NLB adds
this IP address to the TCP/IP stack on the selected interface of all hosts that
are chosen to be part of the cluster, Click Next.
8. In Cluster Parameters, select values in IP Address
and Subnet mask and type the full Internet name
that users will public domain name that users request for access(Its going to
be your NLB cluster name as well). If your are configuring NLB for a website
you can specify that as your website name itself else leave as blank. Microsoft
recommends to use Unicast operation mode for cluster operation, hence leave the
cluster operation mode default and click Next.
9. The
next step defines the most vital part which will help you to define the traffic
across the cluster nodes. If you wish to control the server loads automatically
you can click on Finish which will create
the cluster node now. Let us consider the scenario that either of your server
is having higher hardware configuration and obviously that server will be able
to handle more load, so this can be achieved by defining the port requests. Means,
the request from defined ports will hit to the defined server and the rest will
go to another server. Click on Edit, Now
define the port range that is required
redirect to this host.
In Protocols, select TCP as the specific TCP/IP
protocol that a port rule should cover. Only the network traffic for the
specified protocol is affected by the rule. Traffic not affected by the port
rule is handled by the default host. I would prefer the request through TCP/IP
and UDP to hit on the same server, hence selected as Both.
In Filtering mode, select Multiple host which specifies that multiple hosts in the cluster
handle network traffic for this port rule.
In Affinity ( It is the mode that determines how
the servers are going to balance the load, for more http://technet.microsoft.com/en-in/library/cc733056.aspx
)Select Single and click OK->Finish. Wait for few seconds to complete the configuration.
10. The
below screen describes the steps that will happen during the configuration of
NLB.
Steps 3
to 9 has helped us to create the cluster and one of its host. In a NLB
structure we will have multiple host to handle the traffic and in order to add
the another host,
Right
click on the newly created cluster and select Add
Host To Cluster. The above steps will help you as required(Except step 8
as we have already created the cluster). Once it succeeds you will have the
below structure.
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