Filter
Top Products
55
About Switch Stacking
24/48-Port 10/100 + 4-Port Gigabit Smart Switch with Resilient Clustering Technology and PoE
Appendix B
If the incoming unit did not have an assigned Unit
ID (that is, it was in factory default mode), it will
be assigned the lowest available Unit ID by the
Master. It is strongly recommended that automatic
assigned unit ID mode be used since it provides
better resiliency to the stack.
If the incoming unit already has an assigned Unit ID,
and that Unit ID is unused in the current stack, the
incoming unit will keep its assigned Unit ID and the
Master will apply to it any configuration relevant to
that Unit ID.
If the incoming unit already has an assigned Unit
ID, and that Unit ID conflicts with a unit ID in the
current stack, the Master will reallocate a new
Unit ID to the incoming unit, giving it the lowest
available Unit ID (assuming, of course, that the
incoming unit does not have a manually assigned
Unit ID, which the Master cannot change).
If the incoming unit cannot be assigned an
available Unit ID for any reason (in the case of unit
replacement that can only happen if the incoming
unit has a manually assigned Unit ID), then it will be
effectively shut down—that is, it will not be joined
to the stack.
The stack Master will now carry out Unit and port
configuration for the incoming unit.
Any configuration information the Master has that
is relevant to the number assigned to the incoming
unit will be applied. In particular, if the incoming
unit was assigned the same Unit ID of the unit it
replaces, then it will receive the same configuration
as the failed unit, to the extent possible.
If the incoming unit is identical in makeup to the
replaced unit, the entire configuration of the replaced
unit will be applied to the incoming one and the stack
will go back to the state it was in before unit failure.
However, sometimes the incoming unit is not identical
to the unit that failed in these cases. The stack Master
will apply the configuration in the following manner:
If a 24-port unit replaces a failed 48-port unit,
then the ports of the incoming unit will be
configured according to the way the first 24
ports of the failed unit were configured.
(Note that the configuration of all 48 ports of the
failed unit is remembered, even though only the
first 24 are currently applied. If, in the future, a 48
port unit is inserted and assigned the same Unit
ID, it will be configured as the original failed 48-
port unit was configured).
If a 48-port unit replaces a 24-port unit, then
the first 24 ports of the incoming unit will be
•
•
•
•
3.
•
•
•
configured according to the way the ports of the
failed unit were configured, and the rest of the
ports of the incoming unit will be configured at
default settings.
If the units (the failed one and its replacement)
had/have uplink ports, then the first uplink of
the incoming unit will be configured as was the
first uplink of the failed unit, and so on.
Stack Master Failure and Replacement
In this example, the master unit fails in a running stack.
When notified of the failure, a system administrator
removes the failed unit and replaces it with another one.
When the unit fails, the stack Backup Master detects (via
the ongoing monitoring Master Discovery process) that
the master unit no longer responds and takes over as the
stack master. The backup master directs all other stack
members to route unit-to-unit traffic around the failed
unit using the ring topology of the stacking connections.
At the same time the stack Backup Master notifies the
system administrator (using SYSLOG messages and SNMP
traps) of the failure.
When the failed unit is disconnected from the stack, all
traffic will already be routed around it, and as long as all
other stacking connections are left intact, the stack should
continue to run.
When a new unit is inserted in the stack and powered up,
the following will happen:
The incoming unit will perform Master discovery, and
perhaps participate in a Master Election, as described
above.
If the incoming unit has a Unit ID of 1 or 2 (that
is, the unit is a master-enabled unit), then Master
Election will be initiated. However, since the
running stack Backup Master has a longer run time,
assuming that it has been running for more then 10
minutes, it will remain elected as the stack Master
and the incoming unit will not become a new stack
Master. This may result in an incoming unit using
Unit ID=1, and serving as the stack backup master,
while the already running unit with Unit ID=2
remains the active stack master.
The stack Master at this stage will carry out a Unit ID
allocation and conflict resolution process.
If the incoming unit did not have an assigned Unit
ID (that is, it was in factory default mode), it will
be assigned the lowest available Unit ID by the
Master. It is strongly recommended that automatic
assigned unit ID mode be used since it provides
better resiliency to the stack.
•
1.
•
2.
•