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Network traffic arrives on one of a number of different ports (for example FTP traffic uses ports 20 and 21 while HTTP traffic uses port 80). Network Load Balancing may be configured on a port by port basis or range of ports. For each port three options are available to control the forwarding of the traffic:
* '''Single Host''' - Traffic to the designated port is forward to a singe single node in the cluster.
* '''Multiple Hosts''' - Traffic to the designated port is distributed between the nodes in the cluster.
The ''Priority (unique host ID)'' is a number between 1 and 32 and serves two purposes. Firstly, the number provides a unique ID within the cluster to distinguish the server from other nodes. Secondly, it specifies the priority order of the cluster. The cluster node with the lowest priority is assigned to handle all traffic that is not covered by a ''port rule''. All servers joining a cluster must have a unique ID. A new server attempting to join a cluster with a conflicting ID will be denied membership.
The ''Dedicated IP addresses'' fields are used when a single network adapter is used for both communication between cluster nodes and external network traffic. It is used to specify the host's unique IP address, which is used for non-cluster network traffic (i.e . direct connections to the specific server from outside the cluster without being affected by the Network Load Balancing). This must be a fixed IP address and not a DHCP address and as such should also be entered into the network properties dialog of the node. To configure dedicated IP addresses, click on the ''Add...'' button and enter the IP address and subnet mask (for example 255.255.255.0).
The ''Initial host state'' setting controls the intitial initial state of the node when the systems system is started. The default is for the server to start as an active participant in the cluster. Alternative options are ''Suspend'' and ''Stop''.
Clicking ''Next'' displays the ''Cluster IP addresses'' screen. These are the virtual IP addresses by which the cluster will be accessible on the network. These IP addresses are shared by all nodes in the cluster and a cluster may have multiple virtual IP addresses. Once the cluster IP addresses are specified, click on ''Next'' to proceed to the ''Cluster Parameters'' screen:
On this screen, enter the full internet name of the cluster (for example cluster.techotopia.com) and choose the appropriate ''Cluster operation mode''. As outlined earlier in this chapter, the options here are Unicast, Multicast and IGMP multicast. IGMP multicast IPv4 addreeses addresses are limited to the Class D address range. Once selection is complete, click ''Next'' to proceed to the ''Port Rules'' screen:
By default all TCP and UDP traffic on all ports (0 through 65535) is balanced across all nodes in the cluster with ''single client affinity''. To define new or modify existing rules, for example to direct traffic to a particular port to a specific cluster node, use the ''Add'' and ''Edit'' buttons. Once port rules have been defindeddefined, click ''Finish'' to complete this phase of the configuration process. The Network Load Balancing Manager will now list the new cluster containing the single node as illustrated below:
== Adding and Removing Network Load Balanced Cluster Nodes ==
Before adding a new host to a cluster it is first necesary necessary to install the Network Load Balancing feature on the new server as outlined previously in this chapter.
To add additional nodes to a Network Balanced Cluster, right click on the cluster in the left hand panel of the ''Network Load Balancing Manager'' and select ''Add Host To Cluster''. If no cluster is currently listed, right click on ''Network Load Balancing Manager'' entry and select ''Connect to Existing''. In the connection dialog enter the name or IP address of a node in the cluster (or the IP address of the cluster itself) and click on ''Connect''. Once the connection is established , click on ''Finish'' to return to the manager interface where the cluster will be listed in the left hand panel using the cluster's full internet name.
To add a node, right click on the cluster name and select ''Add Host to Cluster''. In the resulting dialog enter the name or IP address of the host to be added as a new cluster node and click on ''Connect''. Once the connection is established, proceed to the next screen and specify the unique ID/ priority for the new node, together with dedicated IP addresses and the initial host state. Click ''Next'' to change any of the cluster port rule settings. Once finished, the new host will be listed in the manager screen with a status of ''Pending'', followed by ''Converging'' and finally ''Converged''.
Existing nodes in a cluster may be either suspended to or removed. In either case, right click on the node in the ''Network Load Balancing Manager'' and select either ''Suspend'' or ''Delete Host''. A suspended node may be resumed by selecting ''Resume'' from the same menu. A deleted node must be added to the cluster once again using the steps outlined above.
