الجمعة، 8 فبراير 2008

Configuring Windows Network Load Balancing

Configuring Windows Network Load Balancing

Requirements that all servers must meet to use Windows NLB:

  • Have at least one network interface configured for Load Balancing.
  • Use TCP/IP.
  • Be on the same subnet.
  • Share a common (virtual) IP address.

To enable NLB (Control Panel | Network Connections | Right-click on your network card | Properties | Check the box next to the “Network Load Balancing” option).


Once you enable NLB, you must configure it (Network adapter properties | Highlight “Network Load Balancing” | Click the “Properties” button).


Cluster Parameters

§ First enter the virtual IP address

§ Subnet mask

§ DNS name that your cluster will use

.

Host Parameters

§ The “Host Priority” is a unique number assigned to each server in the cluster.

§ Dedicated IP of the Host (it's IP)

§ Subnet mask

Unicast mode, NLB replaces the network card’s original MAC address.

Multicast mode, NLB adds the new virtual MAC to the network card, but also keeps the card’s original MAC address.

In Multicast mode has two MAC addresses that causes some problems that (Most routers reject the ARP replies sent by hosts in the cluster, since the router sees the response to the ARP request that contains a unicast IP address with a multicast MAC address) so, needs to manually configure the ARP entries on the router.


The disadvantage is that since all hosts in the cluster all have the same MAC and IP address, they do not have the ability to communicate with each other via their NLB network card. A second network card is required for communication between the servers.

Port Rules

§ First add a new rule (Port Rules tab | Add button)

§ Configure the port range

§ Select the protocol (TCP or UDP or Both)

§ The filtering mode “Multiple Host”

§ The “Affinity” determines if a specific client’s requests will continue to be routed to a specific server.

o If you’re using the Session Directory then a specification here is not required or can be set to “none

o If you are not using the Session Directory, set this rule to “single affinity” so that a client will always be serviced by the same server and users can reconnect to their disconnected sessions.

§ The “Load weight” setting determines the amount of users/load this server should handle.

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