3Com 7757 Configuration Manual page 706

706 C 63: C
HAPTER LUSTER
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Switch Roles in the
Cluster
You need to enable the cluster function and configure cluster parameters on a
management device. However, you only need to enable the cluster function on
the member devices and candidate devices.
Introduction to function of cluster
Cluster provides the function of batch management for the switches in the
network. Cluster provides external management and maintenance applications,
including SNMP, command line, program and data loading, log report and alarm
report. These applications can be divided into internal-to-external applications and
external-to-internal applications. All the applications are processed according to
the following procedure:
The communication between the management device and member device in
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the cluster is implemented through packet interaction in the management
VLAN.
The communication between the cluster and the external server is
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implemented by the Layer 3 interface of the cluster management VLAN.
When the member device in the cluster communicates with the external server,
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the member device transmits the data to the management device first, and
then the management device transmits the data to the external server. When
the management program running on the external server manages the
member device, the external server transmits the protocol packets to the
management device first, and then the management device forwards the
protocol packets to the member device.
You can configure public FTP servers, TFTP servers, logging hosts and SNMP hosts
for the whole cluster. The management device in the cluster is the default public
FTP server of the cluster when the public FTP server of the cluster is not configured.
Cluster, together with the network management system, can perform large-scaled
device management.
The Switch 7750 manage the cluster with VLAN 1 being the management VLAN in
the cluster. You are required to configure the IP address of the Layer 3 virtual
interface of the management VLAN before setting up a cluster. Otherwise, the
cluster cannot be set up successfully. After the cluster is set up, you are not
allowed to modify the IP address of the management VLAN interface.
According to their functions and status in a cluster, switches in the cluster play
different roles. You can specify the role a switch plays. A switch also changes its
role according to specific rules.
The following three switch roles exist in a cluster: management device, member
device, and candidate device.