Network Load Balancing
Network Load Balancing |
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Although you do not need to change the host parameters according to scenario, you should be aware of the following considerations.
This parameter defines the host's priority in being assigned client requests. The possible values are 1 to 32, inclusive; the lower the integer, the higher the host's priority.
Gaps in the numerical sequence of Host Priority IDs are allowed. This means that if a host from the middle of the sequence of Host Priority IDs goes out of service, the cluster can continue responding to clients.
The Host Priority ID does the following:
Usually, you set the Initial parameter so that Network Load Balancing starts when the host boots. However, if the startup of the service receiving the client traffic is delayed after boot and there are many client requests for Network Load Balancing to distribute as soon as Network Load Balancing starts, a backlog of client requests would form before startup of the service for which Network Load Balancing is handling client requests. An example would be some earlier Web servers. In this case, you can filter traffic by starting Network Load Balancing manually or from a script after starting the service that receives the client requests.
Because each host's dedicated IP address is for network traffic that is not related to client requests to the cluster, Network Load Balancing never filters traffic or applies port rules to this address.
The dedicated IP address is normally the first in the list of IP addresses used by TCP/IP for the host's network connection. This ensures that outbound connections from the host use the dedicated address instead of a virtual IP address for their source address. Otherwise, replies for outbound connections could be load-balanced and delivered to another host.
In certain scenarios (such as load-balancing for virtual private networks), you do not set a dedicated IP address in TCP/IP for the host's network connection. These applications require that the cluster's primary IP address be used for outbound connections. Therefore, in these scenarios you do not need to set a value for this parameter. These scenarios are covered in "Scenarios," later in this chapter.