If the adapter does not support this, you will need to replace the adapter. Futhermore, if you only have one network adapter, you will not be able to communicate to the other servers in the cluster anymore. So if you are forced to use unicast, make sure to use multiple network interface cards, and only apply NLB to one of the cards. The benefit of using unicast is the fact that it works out of the box, with all routers and switches.
After all, every network card has only one MAC address. This is the recommended technique unless you have indications that your network performance has decreased due to NLB multicast traffic.
If your servers have only one network card, you should use multicast. The lower the number, the higher the preference. Just make sure to set a unique host value.
You can set afinity parameters and load weight parameters, which are explained below. Single host : in this scenario, traffic will only be handled by the cluster node with the highest Handling priority ID which is not the same as the host priority ID — this ID is only used for traffic that is not covered by port rules. The handling priority number must be unique on each node. Disable mode : in this scenario, clustering acts as a basic firewall, and will block connections to the ports defined in the rule.
Afinity : Choose this setting based on the ability for an application to maintain state across servers. If the application is not capable of maintaining state, you would want the client to connect to the same server.
Especially http servers have issues with this. None : this is true load balancing. If you application cannot deal with state information that is spread over multiple sessions and servers, then this will break your application.
Single : use this to force clients to use the same server as the previous connection. While traffic from multiple clients will be distributed over multiple cluster nodes, the load may not be spread perfectly, because one client could generate more traffic and sessions than another client. Class C : works in a similar way as "single", but it assigns a cluster node based on an entire class C network.
So if one of the IP addresses in the same class C network has connected, the other ones will connect to the same cluster node You must set the afinity parameters to the same values for each cluster node. Load weigth : Using this parameter, you can define the accepted load on the cluster nodes.
If you have 3 NLB servers, and 2 of them are capable of handling more clients, you could set the load weight to e. The timing is based on the unicast or multicast heartbeat messages that are exchanged in regular intervals. If one of the node does not respond over five consecutive times, a "Convergence" action is initiated. This is the process that exchanges node availability, cluster parameters, host parameters, and port rules between the NLB cluster nodes.
This process should take only a few seconds. Default : decimal. Possible values : between and Default : 5 decimal. You should see all nodes that are part of the cluster. If that is not the case, have a look at the "Known problems" section. Select one of the nodes. If you have just set up the NLB, the hosts may still be "Converging", which means that they are exchanging configurations. If this process has been completed, the nodes should turn Green and should indicate "Converged".
You should be connected to one of the nodes in the cluster. If one of the nodes in the cluster fails, the clients should be connected to one of the other nodes in the cluster.
In the procedure above, I have mentioned a couple of configuration options, which may require a little bit of explanation. ALl cluster nodes are assigned the same MAC address. This technique is used in older versions of NLB. In fact, clients never learn the real MAC address of the cluster, which sometimes results in problems. If you really want to use unicast, you may have to set the following registry key on all members in order to use the real MAC address on outgoing packets :.
Another caveat of using unicast is the fact that the NLB driver will attempt to change the MAC address of the network interface card. If the adapter does not support this, you will need to replace the adapter. Futhermore, if you only have one network adapter, you will not be able to communicate to the other servers in the cluster anymore.
So if you are forced to use unicast, make sure to use multiple network interface cards, and only apply NLB to one of the cards. The benefit of using unicast is the fact that it works out of the box, with all routers and switches.
After all, every network card has only one MAC address. This is the recommended technique unless you have indications that your network performance has decreased due to NLB multicast traffic.
If your servers have only one network card, you should use multicast. The lower the number, the higher the preference. Just make sure to set a unique host value. Filtering mode : Multiple hosts : use this to perform load balancing. You can set afinity parameters and load weight parameters, which are explained below. Single host : in this scenario, traffic will only be handled by the cluster node with the highest Handling priority ID which is not the same as the host priority ID — this ID is only used for traffic that is not covered by port rules.
The handling priority number must be unique on each node. Disable mode : in this scenario, clustering acts as a basic firewall, and will block connections to the ports defined in the rule.
Afinity : Choose this setting based on the ability for an application to maintain state across servers. If the application is not capable of maintaining state, you would want the client to connect to the same server. Especially http servers have issues with this. None : this is true load balancing. If you application cannot deal with state information that is spread over multiple sessions and servers, then this will break your application. Single : use this to force clients to use the same server as the previous connection.
While traffic from multiple clients will be distributed over multiple cluster nodes, the load may not be spread perfectly, because one client could generate more traffic and sessions than another client. Class C : works in a similar way as "single", but it assigns a cluster node based on an entire class C network. So if one of the IP addresses in the same class C network has connected, the other ones will connect to the same cluster node.
Using this parameter, you can define the accepted load on the cluster nodes. If you have 3 NLB servers, and 2 of them are capable of handling more clients, you could set the load weight to e. When you change something in the cluster node configurations, the changes are picked up dynamically by the other nodes. The timing is based on the unicast or multicast heartbeat messages that are exchanged in regular intervals. If one of the node does not respond over five consecutive times, a "Convergence" action is initiated.
This is the process that exchanges node availability, cluster parameters, host parameters, and port rules between the NLB cluster nodes. This process should take only a few seconds. Default : decimal. Possible values : between and Default : 5 decimal. Possible values : between 5 and When a node has become unreachable, and if you open the nlbmgr. Useful resources blog deployment guide. Read blog. Administration manual Read manual. Build a web farm with IIS servers Read other.
Configure IIS web farm load balancing Read other. Get started. Get in touch Start a conversation about the right solution for your business.
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