Network Load Balancing Manager Properties

Cluster IP addresses

The IP address parameter specifies the cluster's primary IP address. IPv4 addresses use the standard Internet dotted notation (for example, w.x.y.z). IPv6 addresses use 16-byte addresses, typically expressed in colon-hexadecimal notation. Colon-hexadecimal notation uses eight 4-digit hexadecimal numbers, with colons separating the 16-bit blocks (the 4-digit numbers).

To manage addresses more easily, IPv6 suppresses leading zeros and compresses a single contiguous all-zero 16-bit block, represent the contiguous block with two colons (::). This is known as double-colon compression. An example of an IPv6 address with leading zeros suppressed is:

FEC0:0:0:0:2AA:FF:FE3F:2A1C

The address is a virtual IP address, and it must be set identically for all hosts in the cluster. This IP address is used to address the cluster as a whole, and it should be the IP address that maps to the full Internet name that you specify for the cluster.

If you want to add multiple IP addresses to the cluster, click Add to enter the additional IP addresses. If you are configuring a virtual private network (VPN) load-balancing cluster, you should not configure the dedicated IP address. On a VPN, only the cluster IP address should be present on each of the cluster hosts.

Port rules

The Port Rules tab shows only the summary of existing port rules. If you click Add or Edit, the following parameters will be available:

• The Cluster IP address parameter specifies the cluster IP address that the port rule should cover. If this parameter is left blank and All is selected, the port rule is a global port rule, and it will cover all cluster IP addresses associated with that particular NLB cluster. If a cluster IP address is specified, the port rule overrides any conflicting global port rule for that particular cluster IP address.
  
  
• The Port range parameter specifies the TCP/UDP port range that a port rule should cover. The default port range is 0 to 65,535. Rules for a single port are encoded as a range having the same starting and ending port numbers.
  
  
• The Protocols parameter lets you choose the specific TCP/IP protocol that a port rule should cover: TCP, UDP, or both. Only the network traffic for the specified protocol is affected by the rule. Traffic that is not affected by the port rule is handled by the default host.
  
  
• For Filtering mode, configure the following parameters:
  
  
  • The Multiple hosts parameter specifies that multiple hosts in the cluster will handle network traffic for the associated port rule. This filtering mode provides scaled performance and fault tolerance by distributing the network load among multiple hosts. You can specify that the load be equally distributed among the hosts or that each host will handle a specified load weight.
    
    
  • The Single host parameter specifies that network traffic for the associated port rule be handled by a single host in the cluster according to the specified handling priority. This filtering mode provides port specific fault tolerance for handling network traffic.
    
    
  • The Disable this port range parameter specifies that all network traffic for the associated port rule be blocked. In this case, the NLB driver filters all corresponding network packets or datagrams. This filtering mode lets you block network traffic that is addressed to a specific range of ports.
    
    
• The Affinity parameter is applicable only for the Multiple hosts filtering mode.
  
  
  • The None option specifies that multiple connections from the same client IP address can be handled by different cluster hosts (there is no client affinity). To allow Network Load Balancing to properly handle IP fragments, you should avoid using None when selecting UDP or Both for your protocol setting.
    
    
  • The Single option specifies that NLB should direct multiple requests from the same client IP address to the same cluster host. This is the default setting for affinity. You can optionally modify the NLB client affinity to direct all client requests from a TCP/IP Class C address range (instead of a single IP address) to a single cluster host by enabling the Network option instead of the Single option. This feature ensures that clients that use multiple proxy servers to access the cluster can have their TCP connections directed to the same cluster host.
    
    
  • The Network option specifies that NLB direct multiple requests from the same TCP/IP Class C address range to the same cluster host. Enabling Network affinity instead of Single affinity ensures that clients that use multiple proxy servers to access the cluster have their TCP connections directed to the same cluster host.
    
    The use of multiple proxy servers at the client's site causes requests from a single client to appear to originate from different computers. Assuming that all of the client's proxy servers are located within the same address range, Network affinity ensures that client sessions are properly handled. If you do not need this capability, use Single affinity to maximize scaled performance.
    
    
  As an extension to the Single and Network options, you can configure a time-out setting to preserve client affinity when the configuration of an NLB cluster is changed. This extension also allows clients to keep affinity to a cluster host even if there are no active, existing connections from the client to the host.
  
  Enabling Single or Network affinity ensures that only one cluster host handles all connections that are part of the same client session. This is important if the server application that is running on the cluster host maintains a session state (such as server cookies) between connections.
  
  This does not preserve a session state with back-end databases where many different transactions are occurring that involve many different computers. When the connection ends, the session state also ends.
  
  Disabling affinity allows for improved load balancing because it allows multiple connections from the same client to be handled concurrently by different cluster hosts. To maximize scaled performance, disable the client affinity (by using the None option) when it is not needed. However, to allow NLB to properly handle IP fragments, you should avoid using None when selecting UDP or Both for your protocol setting.
  
  

• The Load weight parameter is applicable only for the Multiple hosts filtering mode. You can configure this parameter only when you open the port rules dialog box through Host Properties. (This parameter is not configurable when you open the port rules dialog box through Cluster Properties.)
  
  When using the Multiple hosts filtering mode, this parameter specifies the relative amount of load-balanced network traffic that this host should handle for the associated port rule. Allowed values range from 0 (zero) to 100. To prevent a host from handling any network traffic, set the load weight to 0 (zero). The actual fraction of traffic handled by each host is computed as the local load weight divided by the sum of all load weights across the cluster.
  
  You can specify different load weights for each host in the cluster by using the Load weight parameter. You can specify that all hosts distribute the network load equally by using the Equal load distribution parameter instead of the Load weight parameter.
  
  
• The Handling priority parameter is applicable only for Single host filtering mode. You can configure this parameter only when you open the port rules dialog box through Host Properties. (This parameter is not available when you open the port rules dialog box through Cluster Properties.)
  
  When Single host filtering mode is used, the Handling priority parameter specifies the local host's priority for handling the network traffic for the associated port rule. The host with the highest handling priority (lowest numerical value) for this rule among the current members of the cluster will handle all of the traffic for this rule. The allowed values range from 1, the highest priority, to the maximum number of hosts allowed (32). This value must be unique for all hosts in the cluster. Although this parameter is displayed in the Defined port rules list, you configure this parameter on the Host Parameters tab.