DUA1640-5AAA02
2-4 CHAPTER 2: HOW THE PS HUBS DIFFER
■If a 10Mbps transceiver module is fitted or no transceiver module
is fitted, the segment switch is in 802.1d Bridge m ode — All
packets with an unknown destination address are forwarded to
all ports.
Default Settings
The PS Hub 50 comes ready to use with all of the cascaded segments
connected to its segment switch (the default co nfiguration). To isolate
and connect segments, and to control the way the hub’s segment
switch works, you must manage the hub. For information on
management, refer to Chapter 5.
Multiple PS Hub 50 Units in a Stack
The PS Hub 50 has been designed so that you can have multiple
PS Hub 50 units in the same stack. You may want to do this so that the
cascaded segments are always switched, when:
■The stack is split.
■One of the PS Hub 50 units is removed or fails.
You could have two PS Hub 50 units in a stack of PS Hubs, one a t the
top and one at the bottom.
PS Hub 50 units automatically detect each other in the stack and
configure themselves so that one of the hubs becomes the active
switch, and the segment switches in all the other hubs are disabled.
This is to reduce the possibility of loops in the stack. If a PS Hub 50 is
removed from the stack or fails, the other hubs reconfigu re themselves.
The process for detecting and reconfiguring is as follows:
1If one hub has a 100Mbps transceiver modul e fitted, that hub becomes
the active switch.
2If more than one hub has a 100Mbps transcei ver module fitted but
only one has a link (is receiving information th rough its transceiver
module port), that hub becomes the active swi tch.
3If all PS Hub 50 units appear to be equal, the hub with the l owest unit
number (the one nearest the bottom of the stack if connected
correctly) becomes the active switch.
Only the active switch learns addresses and adds them to its switch
database.