Specifications

48 ExtremeWare XOS 11.0 Concepts Guide
Managing the Switch
Node Election
Node election is based on leader election between the MSMs installed in the chassis. The MSM installed
in slot A has master status. The Device Manager collects the node health information and forwards that
information to the Node Manager. The Node Manager then computes the quality of the node which is
later used in leader election.
When two nodes exchange their health information, they determine the healthier node. Based on the
election results obtained from all of the nodes, the healthiest node wins the election criteria.
At the end of the election process, a master is selected. The master MSM runs the switch management
functions, and the backup MSM is available if the master fails.
Determining the Master Node
The master node is determined by the following parameters:
• Node state—The node state must be STANDBY to participate in leader election and be selected
master. If the node is in the INIT, DOWN, or FAIL states, it cannot participate in leader election. For
more information about the node states, see “Viewing Node Status” on page 51.
• Configuration priority—This is a user assigned priority. The configured priority is compared only
after the node meets the minimum thresholds in each category for it to be healthy. Required
processes and devices must not fail.
• Software health—This represents the percent of processes available.
• Health of secondary hardware components—This represents the health of the switch components,
such as power supplies, fans, and so forth.
• Slot ID—The MSM slot where the node is installed (MSM-A or MSM-B).
Configuring the Node Priority
To configure the priority of an MSM node, use the following command:
configure node slot <slot_id> priority <node_pri>
If you do not configure any priorities, MSM-A has a higher priority than MSM-B. For the slot_id
parameter, enter A for the MSM installed in slot A or B for the MSM installed in slot B. By default, the
priority is 0. The lower the value, the higher the priority.
Master The master MSM provides all of the switch management functions including bringing up and
programming the I/O modules, running the bridging and routing protocols, and configuring the
switch.
Node A node runs the XOS management applications on the switch. Each MSM installed in the
chassis is a node.
Node election The process of electing the master and backup nodes is called node election. To determine the
master, the Node Manager sends hello messages to all of the nodes in the system, computes
the health of the system, and checks the parameters of each node (such as the node state,
configuration, priority, and so forth.).
If only one MSM is installed, it becomes the master MSM.
Node Manager The Node Manager performs the process of node election.
Standby The standby MSM is in neither the backup or master mode of operation.
Table 10: System redundancy terms (continued)
Term Description