Today we going to look setup Network Load Balanced Clusters in Windows Server 2008 R2. NLB provides high availabilty and scability for IP based traffic for TCP, UDP and GRE (General Routing Encapsulation). In server 2008 you can build NLB cluster with two node/host with max upto 32 nodes/hosts.
Now Lets start building our NLB. Install Network Load Balancing Feature using Server Manager.
Once the feature is installed we would be adding Nodes to the clusters
Client affinity involves the tracking of both destination port and source IP address information to optionally ensure that all traffic to a specific port from a client is directed to the same server in the cluster. The available Client affinity settings are as follows:
Multicast—Multicast mode allows communication among hosts because it adds a Layer 2 multicast address to the cluster instead of changing the cluster. Communication among hosts is possible because the hosts retain their original unique media access control (MAC) addresses and already have unique, dedicated IP addresses. However, the address resolution protocol (ARP) reply that is sent by a host in the cluster (in response to an ARP request) maps the cluster’s unicast IP address to its multicast MAC address. Some routers do not support the resolution of unicast IP addresses to multicast MAC addresses, and they discard the ARP reply.
As a result, an administrator must add a static ARP entry in the router, mapping
the cluster IP address to its MAC address.
The cluster operation mode parameters specify whether a multicast media access control (MAC) address should be used for cluster operations. If multicast is enabled, NLB converts the cluster MAC address for the cluster adapter into a multicast address. It also ensures that the cluster's primary IP address resolves to this multicast address as part of the Address Resolution Protocol (ARP). The adapter can now use its original, built-in MAC address that was disabled in unicast mode.
You must first enable multicast support before enabling Internet Group Management Protocol (IGMP) support. IGMP support can also be enabled on the network adapter.
The IGMP multicast check box enables IGMP support for limiting switch flooding by limiting traffic to "Network Load Balancing ports" only. That is, enabling IGMP support ensures that traffic intended for an NLB cluster passes through only those ports serving the cluster hosts and not all switch ports.
Additional Consideration for the NLB cluster
When you create an NLB cluster, NLB is automatically bound to each of the network adapters in the cluster.
When you add additional hosts after the first host is added, the subsequent hosts will automatically inherit the cluster port rules from the initial host.
The new cluster host will not immediately be in a running state in the cluster. The new host settings must first be circulated through all cluster hosts.
The four basic Network Load Balancing modes are as follows:
· Unicast with Single Network Adapter - The MAC address of network adapter is disabled and the cluster MAC address is used. Traffic is received by all nodes in the cluster and filtered by the NLB driver. Nodes in the cluster are able to communicate with addresses outside the cluster subnet, but node to node communication within cluster subnet is not possible.
· Unicast with Multiple Network Adapters - The MAC address of the network adapter is disabled and the cluster MAC address is used. Traffic is received by all nodes in the cluster and filtered by the NLB driver. Nodes within the cluster are able to communicate with each other within the cluster subnet and also with addresses outside the subnet.
· Multicast with Single Network Adapters - Both network adapter and cluster MAC addresses are enabled. Nodes within the cluster are able to communicate with each other within the cluster subnet and also with addresses outside the subnet. Not recommended where port rules are configured to direct significant levels of traffic to specific cluster nodes.
· Multicast with Multiple Network Adapters - Both network adapter and cluster MAC addresses are enabled. Nodes within the cluster are able to communicate with each other within the cluster subnet and also with addresses outside the subnet. This is the ideal configuration for environments where there are significant levels of traffic directed to specific cluster nodes.
Now Lets start building our NLB. Install Network Load Balancing Feature using Server Manager.
Once the feature is installed we would be adding Nodes to the clusters
Add Cluster IP
Client affinity involves the tracking of both destination port and source IP address information to optionally ensure that all traffic to a specific port from a client is directed to the same server in the cluster. The available Client affinity settings are as follows:
- Single - Requests from a single source IP address are directed to the same cluster node.
- Network - Requests originating from within the same Class C network address range are directed to the same cluster node.
- None - No client affinity. Requests are directed to nodes regardless of previous assignments.
Multicast—Multicast mode allows communication among hosts because it adds a Layer 2 multicast address to the cluster instead of changing the cluster. Communication among hosts is possible because the hosts retain their original unique media access control (MAC) addresses and already have unique, dedicated IP addresses. However, the address resolution protocol (ARP) reply that is sent by a host in the cluster (in response to an ARP request) maps the cluster’s unicast IP address to its multicast MAC address. Some routers do not support the resolution of unicast IP addresses to multicast MAC addresses, and they discard the ARP reply.
As a result, an administrator must add a static ARP entry in the router, mapping
the cluster IP address to its MAC address.
The cluster operation mode parameters specify whether a multicast media access control (MAC) address should be used for cluster operations. If multicast is enabled, NLB converts the cluster MAC address for the cluster adapter into a multicast address. It also ensures that the cluster's primary IP address resolves to this multicast address as part of the Address Resolution Protocol (ARP). The adapter can now use its original, built-in MAC address that was disabled in unicast mode.
You must first enable multicast support before enabling Internet Group Management Protocol (IGMP) support. IGMP support can also be enabled on the network adapter.
The IGMP multicast check box enables IGMP support for limiting switch flooding by limiting traffic to "Network Load Balancing ports" only. That is, enabling IGMP support ensures that traffic intended for an NLB cluster passes through only those ports serving the cluster hosts and not all switch ports.
Additional Consideration for the NLB cluster
When you create an NLB cluster, NLB is automatically bound to each of the network adapters in the cluster.
When you add additional hosts after the first host is added, the subsequent hosts will automatically inherit the cluster port rules from the initial host.
The new cluster host will not immediately be in a running state in the cluster. The new host settings must first be circulated through all cluster hosts.
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