Windows Server 2008 R2 Unleashed (240 page)

serves up static pages, can respond to a single client’s requests from multiple nodes in the

NLB cluster. For a web-based application, such as an e-commerce application, an

encrypted SSL session, or an application that is authenticated by the actual web server, the

NLB cluster would need to direct all communication between the client and a specific

cluster node. Considering these types of scenarios in advance helps determine how the

NLB cluster will be defined.

1216

CHAPTER 29

System-Level Fault Tolerance (Clustering/Network Load Balancing)

Installing the Network Load Balancing Feature

Before an NLB cluster can be created, the feature needs to be installed on all servers that

will participate in the cluster. To install the Network Load Balancing feature, perform the

following steps:

1. Log on to each Windows Server 2008 R2 system with an account that has local

administrator rights.

2. Click Start, click All Programs, click Administrative Tools, and select Server Manager.

3. In the tree pane, select Features, and in the Actions pane, click the Add Features link.

4. On the Before You Begin page, click Next to continue.

5. On the Add Features page, check the box for Network Load Balancing, and click

Next to continue.

6. On the Confirm Installation Selections page, review the list of features that will be

added, and click Install to begin the installation.

7. On the Installations Results page, review the results, and click Close to return to

Server Manager.

8. Close the Server Manager console and log off of the server.

9. Log on and repeat this process on the remaining servers that will participate in the

ptg

cluster as required.

Creating Port Rules

When an NLB cluster is created, one general port rule is also created for the cluster. The

NLB cluster port rule or rules define what type of network traffic the cluster will load-

balance across the cluster nodes and how the connections will be managed. The Port Rules

Filtering option defines how the traffic will be balanced across each individual node. As a

best practice, limiting the allowed ports for the clustered IP addresses to only those needed

by the cluster load-balanced applications can improve overall cluster performance and

security. In an NLB cluster, because each node can answer for the clustered IP address, all

inbound traffic is received and processed by each node. When a node receives the request,

it either handles the request or drops the packet if another node has already established a

session or responded to the initial request.

When an administrator discards the default NLB cluster port rule and creates a rule that

only allows specific ports to the clustered IP address or addresses, plus an additional rule

to block all other traffic destined for the cluster IP address, each cluster node can quickly

eliminate and drop packets that do not meet the allow port rule and in effect improve

network performance of the cluster. The security benefit of this configuration also removes

any risk of attacks on any other port using the cluster IP address.

Port Rules Filtering Mode and Affinity

Within an NLB cluster port rule, the NLB administrator must configure the appropriate

filtering mode. This allows the administrator to specify whether only one node or multi-

ple nodes in the cluster can respond to requests from a single client throughout a session.

There are three filtering modes: Single Host, Disable This Port Range, and Multiple Host.

Deploying Network Load Balancing Clusters

1217

Single Host Filtering Mode

The Single Host filtering mode ensures that all traffic sent to the cluster IP address that

matches a port rule with this filtering mode enabled is handled exclusively in the cluster

by one particular cluster node.

Disable This Port Range Filtering Mode

The Disable This Port Range filtering mode tells the cluster which ports are not active on

the cluster IP address. Any traffic requests received on the cluster IP address that match a

port rule with this filtering mode result in the network packets getting automatically

discarded or dropped. Administrators should configure specific port rules and use this

filter mode for ports and port ranges that do not need to be load-balanced across the

cluster nodes.

Multiple Hosts Filtering Mode

The Multiple Host filtering mode is probably the most commonly used filtering mode and

is also the default. This mode allows traffic to be handled by all the nodes in the cluster.

When traffic is balanced across multiple nodes, the application requirements define how

the Affinity mode should be set. There are three types of multiple host affinities:

.
None—
This affinity type can send unique clients’ requests to all the servers in the

cluster during the entire span of the session. This can speed up server response times

ptg

but is well suited only for serving static data to clients. This affinity type works well

for general web browsing, read-only file data, and FTP servers.

.
Network—
This affinity type routes traffic from a particular class C address space to

a single NLB cluster node. This mode is not used too often but can accommodate

client sessions that use stateful applications and when different client requests are

serviced by down-level proxy servers. This is a useful affinity type for companies that

direct traffic from several remote offices, through proxies before connecting to the

services, and/or applications managed by the port rules in the NLB cluster.

.
Single—
This affinity type is the most widely used. After the initial request is

received by the cluster nodes from a particular client, that node will handle every

request from that client until the session is completed. This affinity type can accom-

modate sessions that require stateful data such as an encrypted SSL web application

29

or a Remote Desktop session. This is the default filtering mode on a port rule and is

well suited to handle almost any NLB clustered service or application.

Using Cluster Operation Mode

There are three different cluster operation modes: Unicast, Multicast, and IGMP Multicast.

Most traditional network traffic is unicast traffic where clients and servers maintain a one-

to-one network connection. Multicast networking allows a server to send out information

to one multicast address that is then processed by a number of clients. To receive multi-

cast data, a client joins a multicast group associated with the multicast address and one

data feed or transmission is presented to the group by the server, thereby streamlining and

improving network performance of the application. Multicast traffic is usually one direc-

tion and when the multicast client joins the group, it begins to receive the transmission.

1218

CHAPTER 29

System-Level Fault Tolerance (Clustering/Network Load Balancing)

Common applications that use multicast are streaming music and video websites, Internet

radio, and Internet training or online noninteractive courses. IGMP Multicast can be used

in place of multicast and enhances overall network performance when multicast is

required. Selecting this management protocol allows for the multicast clients to register

with the IGMP Multicast server and afterward, the multicast traffic will only be sent to the

switch ports or trunks that connect to the multicast clients, reducing traffic on the

remaining ports of the network switches. One more important point to mention about

multicast traffic is that the network switches and routers that the traffic will pass through

must support multicast traffic and allow it. Many enterprise class switches and routers

have multicast support disabled by default.

Configuring Network Cards for NLB

Configuring the network cards on the NLB cluster nodes is the first step in building the

cluster. Although these steps can be performed during cluster creation using the NLB

Manager, the same result can be achieved by editing the TCP/IP properties of each of the

cluster node’s network cards. Best practice for NLB cluster nodes running in Unicast mode

is to have two network cards to allow host communication to occur on one NIC while

cluster communication is isolated on the cluster NIC. Multiple NICS can also add greater

flexibility when it comes to controlling traffic and managing network security.

ptg

Creating an NLB Cluster

Before an NLB cluster can be created, a few bits of information are required. The NLB

cluster is actually clustering based on a defined IP address, the DNS name, and the TCP/IP

ports that will be used. Each NLB cluster node can also be configured with multiple

network cards. Each card can be associated with a different NLB cluster and a single card

can support multiple clusters, but each cluster must have a different DNS name and IP

address(es). One configuration that cannot be performed is creating a single NLB cluster

that uses multiple network adapters in a single node. To designate multiple adapters for a

single NLB cluster, third-party network teaming software must be loaded prior to configur-

ing the NLB cluster; the cluster will use the Virtual Team Network adapter and the teamed

physical adapters should not be configured with NLB. For this example, a new NLB cluster

will be created for the name www.companyabc.com using the IP address of

192.168.206.50. To create an NLB cluster, perform the following steps:

1. Log on to a Windows Server 2008 R2 system with an account that has local adminis-

trator rights and that has the NLB feature already installed.

2. Click Start, click All Programs, click Administrative Tools, and select Network Load

Balancing Manager.

3. When the Network Load Balancing Manager console opens, click the Cluster menu,

and select New to create a new cluster.

Deploying Network Load Balancing Clusters

1219

4. When the New Cluster window opens, type in the name of the first server that will

be added to the new NLB cluster, and click Connect. If the server is a remote system

and cannot be contacted, ensure that the Inbound Remote Administration exception

has been enabled in the remote system’s firewall.

5. When the server is contacted, each of the network adapters will be listed, select the

adapter that will be used for the NLB cluster, as shown in Figure 29.16, and click Next.

ptg

FIGURE 29.16

Selecting the network adapter that will be used for the NLB cluster.

6. On the Host Parameters page, accept the defaults of giving this first server the Host

ID of 1 and select the dedicated IP address that will be used when communication

is received for the NLB cluster IP address, which will be specified next. Click Next

to continue.

7. On the Cluster IP Addresses page, click the Add button to specify an IPv4 address

and subnet mask or an IPv6 address to use for the NLB cluster, and click OK. For our

example, we will use the IPv4 configuration of 192.168.206.50/255.255.255.0.

29

8. Back on the Cluster IP Addresses page, add additional cluster IP addresses as

required, and click Next to continue.

9. On the Clusters Parameters page, enter the fully qualified DNS name that is associ-

ated with the IP address specified on the previous page, and select whether it will be

used for Unicast traffic, Multicast traffic, or IGMP Multicast. This choice depends on

the network communication of the service or application that will be used in this

NLB cluster. For this example, we are creating an NLB cluster for standard web

traffic, so we will use www.companyabc.com as the Internet name and select Unicast

as the cluster operation mode, as shown in Figure 29.17.