Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 2130)

VCStack Introduction
Software Reference for x310 Series Switches
82.16 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
Disabled Master Monitoring (DMM)
The stack resiliency link and disabled master state offer a unique prevention of
catastrophic network connectivity problems. However, when stack members become
separated, the network is still left in a fragile state where the stack master no longer has
the redundancy of a backup stack member. If the original stack master were to
subsequently fail whilst the stack was separated, then all network connectivity would be
lost if the disabled master’s switchports remained shutdown.
The Disabled Master Monitoring (DMM) feature avoids this situation by continuing to
monitor the status of the original stack master (the active master) via the stack resiliency
link. When the DMM feature is enabled, the disabled master can detect a failure of the
original stack master within a few seconds. If a failure is detected, the disabled master
transitions to the active master state and automatically re-enables all its switchports. This
allows traffic forwarding via the stack to continue.
For more information about the disabled master state, see the section “Disabled Master”
on page 82.15 . Note that a disabled master has the same configuration as an active
master, but a disabled master has all its links shutdown.
To enable the DMM feature, use the commands:
To disable the DMM feature, use the commands:
To show the status of DMM on the VCStack, use the command:
Table 82-2: Stack behavior comparison
Stack behavior with DMM disabled Stack behavior with DMM enabled
■ The VCStack breaks with the Stack
Resiliency Link configured and
enabled. ■ The VCStack breaks with the Stack
Resiliency Link configured and
enabled.
■ The separated stack member becomes
a disabled master. ■ The separated stack member
becomes a disabled master.
■
The disabled master does not monitor
the active master.
■
The disabled master monitors the
active master.
■
If the active master fails then the
disabled master does not become the
active master (no state transition).
■
If the active master fails then the
disabled master becomes the active
master (disabled to active transition).
■
No switchports are re-enabled on the
disabled master. No traffic is
forwarded.
■
Switchports on the disabled master
are re-enabled. Traffic is still
forwarded,
awplus# configure terminal
awplus(config)# stack disabled-master-monitoring
awplus# configure terminal
awplus(config)# no stack disabled-master-monitoring
awplus# show stack [detail]