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Single network adapter in multicast mode

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Single network adapter in multicast mode

This model is suitable for a cluster in which ordinary network communication among cluster hosts is necessary or desirable but in which there is limited dedicated traffic from outside the cluster subnet to specific cluster hosts.

Advantages

  • Only one network adapter is required. It is not necessary to install a second adapter.

  • This model permits ordinary network communication among cluster hosts.

  • You can enable Internet Group Management Protocol (IGMP) support on the cluster hosts to control switch flooding when operating in multicast mode. For more information, see Limit switch port flooding.

Disadvantages

  • Network Load Balancing itself does not affect network performance and a second network adapter is not a requirement. However, under certain conditions, a second adapter can improve overall network performance.

  • Some routers might not support the use of a multicast media access control (MAC)address. This only affects the Network Load Balancing/MAC address (not all MAC addresses) and only when dynamic ARP replies are sent by the cluster to the router, not all MAC addresses.

In this model, the computer can also handle traffic from inside the subnet if the IP datagram does not carry the same MAC address as on the cluster adapter. For more information, see Address Resolution Protocol (ARP).

Regardless of the number of network adapters you use and how the adapters are configured, the cluster heartbeat traffic always originates from the network load balancing network adapter.

Important

  • Network Load Balancing does not support a mixed unicast/multicast environment within a single cluster. Within each cluster, all network adapters in that cluster must be either multicast or unicast; otherwise, the cluster will not function properly.

    There is no restriction on the number of network adapters that can be bound to network load balancing on each computer: Different hosts can have a different number of adapters, but you can never have more than one adapter on a computer be part of the same cluster.

    Different adapters on each computer can be part of different clusters, and they can all reside on the same subnet. You can also host multiple clusters on the same network adapter. For more information, see Understanding virtual clusters.

  • Before you install Network Load Balancing, it is vital that you review Checklist: Enabling and configuring Network Load Balancing, including the sections on cluster parameters, host parameters, and port rules. It is highly recommended that you read through these sections before configuring Network Load Balancing.

For more information, see Single network adapter, Single network adapter limitations, and Using a router in Network Load Balancing system requirements.