TMS zl Management and Configuration Guide ST.1.1.100430
8-4
High Availability
Overview
2. The participant becomes the master, and a gratuitous ARP (Address
Resolution Protocol) message is broadcast to the end nodes and routers
to update their ARP tables to associate the cluster’s IP addresses with the
new master’s MAC addresses.
If the original participant (now the master) reboots while original master
is still offline, you will not lose your configuration. When the original
participant comes back online it will have the same configuration.
3. When the original master comes back online it becomes the participant,
regardless of the specified priority.
For example, suppose that module A is the master (with priority 255) and
module B is the participant (with priority 1). Module A fails, so module B
becomes the master. Some time later, module A comes back online. At
this point, module B remains the master (with priority 1) and module A
becomes the participant (with priority 255). Module B will be the master
until it fails.
Priority becomes important only when both modules come online at the
same time, such as when their host switch is rebooted.
Configuration and Boot Order for HA Members
The order in which you configure and reboot the members of an HA cluster
is extremely important. The cluster member that comes online first will be the
master, and the module that comes online second will be the participant,
regardless of the priority that you have specified.
■ HA cluster members behave according to these rules:
■ The cluster member that comes online first is the cluster master.
■ When another cluster member begins to come online, it detects the cluster
master and reboots, using the cluster master’s startup-config as its own.
When it comes online again, it is the cluster participant.
■ The TMSVLAN settings that were configured on the cluster participant
before becoming a cluster member are permanently erased.
■ When the cluster master fails, the cluster participant becomes the cluster
master without significant interruption.
■ When the former cluster master comes back online, it uploads the startup-
config of the current cluster master and becomes the cluster participant.