Recovering From Stack Failure Or Topology Change; Broken Link For Line And Wrap-Around Topologies - SMC Networks TigerStack II SMC8848M Management Manual

Recovering from Stack Failure or Topology Change

When a link or unit in the stack fails, a trap message is sent and a failure
event is logged. The stack will be rebooted after any system failure or
topology change. It takes two to three minutes to for the stack to reboot. If
the Master unit fails, the backup unit will take over operations as the new
Master unit, reboot the stack, and then select another backup unit after the
stack finishes rebooting. Also note that powering down a unit or inserting
a new unit in the stack will cause the stack to reboot. If a unit is removed
from the stack (due to a power down or failure) or a new unit added to the
stack, the original unit IDs are not affected after rebooting, and a new unit
is assigned the lowest available unit ID.

Broken Link for Line and Wrap-around Topologies

All units in the stack must be connected via stacking cable. You can
connect the units in a simple cascade configuration from the top to the
bottom unit. Using this kind of line topology, if any link or unit in the stack
fails, the stack will be broken in two. The Stack Link LED on the unit that
is no longer receiving traffic from the next unit up or down in the stack
will begin flashing to indicate that the stack link is broken.
When the stack fails, a Master unit is selected from the two stack segments,
either the unit with the Master button depressed, or the unit with the
lowest MAC address if the Master button is not depressed on any unit. The
stack reboots and resumes operations. However, note that the IP address
will be the same for any common VLANs (with active port connections)
that appear in both of the new stack segments. To resolve the conflicting
IP addresses, you should manually replace the failed link or unit as soon as
possible. If you are using a wrap-around stack topology, a single point of
failure in the stack will not cause the stack to fail. It would take two or
more points of failure to break the stack apart.
Note: If a stack breaks apart, the IP address will be the same for any
common VLANs (with active port connections) that appear in
both stack segments.
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