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# Clusters

Column Display Related Tasks Related Topics

This page summarizes the clusters that have been configured in the current WebLogic Server domain.

A cluster defines groups of WebLogic Server servers that work together to increase scalability and reliability.

A cluster appears to clients to be a single WebLogic Server instance. The servers that constitute a cluster can run on the same machine, or be located on different machines.

#### Column Display

You can show fewer or additional data points on this page by expanding Customize this table and modifying the Column Display list. Each data point displays in its own table column.

The following table lists all of the data points that you can display in columns on this page.

Name | Description
--- | ---
Name | The name that you specified when you created the cluster.
Cluster Address | The address that forms a portion of the URL a client uses to connect to this cluster, and that is used for generating EJB handles and entity EJB failover addresses. (This address may be either a DNS host name that maps to multiple IP addresses or a comma-separated list of single address host names or IP addresses.) Defines the address to be used by clients to connect to this cluster. This address may be either a DNS host name that maps to multiple IP addresses or a comma separated list of single address host names or IP addresses. If network channels are configured, it is possible to set the cluster address on a per channel basis. MBean Attribute: `ClusterMBean.ClusterAddress` Changes take effect after you redeploy the module or restart the server.
Multicast Address | The multicast address used by cluster members to communicate with each other. The valid range is from from 224.0.0.0 to 239.255.255.255. The default value used by WebLogic Server is 239.192.0.0. You should avoid using multicast addresses in the range x.0.0.1 This address should be unique to this cluster and should not be shared by other applications. MBean Attribute: `ClusterMBean.MulticastAddress` Changes take effect after you redeploy the module or restart the server.
Multicast Port | The multicast port (between 1 and 65535) used by cluster members to communicate with each other. Defines the multicast port used by cluster members to communicate with each other. MBean Attribute: `ClusterMBean.MulticastPort` Minimum value: `1` Maximum value: `65535` Changes take effect after you redeploy the module or restart the server.
Multicast TTL | The number of network hops (between 1 and 255) that a cluster multicast message is allowed to travel. Defines the number of network hops that a cluster multicast message is allowed to travel. 1 restricts the cluster to one subnet. MBean Attribute: `ClusterMBean.MulticastTTL` Minimum value: `1` Maximum value: `255` Changes take effect after you redeploy the module or restart the server.
Default Load Algorithm | The algorithm to be used for load-balancing between replicated services if none is specified for a particular service. The `round-robin` algorithm cycles through a list of WebLogic Server instances in order. `Weight-based` load balancing improves on the round-robin algorithm by taking into account a pre-assigned weight for each server. In `random` load balancing, requests are routed to servers at random. Defines the algorithm to be used for load-balancing between replicated services if none is specified for a particular service. MBean Attribute: `ClusterMBean.DefaultLoadAlgorithm`

Related Tasks

- Configure clusters
- Assign servers to clusters
- Configure server migration in a cluster
- Configure cross-cluster replication

Related Topics

- Setting up Weblogic Clusters
- Understanding Cluster Configuration and Application Deployment