3Com 3C16405, User Manual

Page: 56 / 188

DUA1640-5AAA02
3-16
C
HAPTER
3: U
SING THE
PS H
UB
Connecting
Different Hubs
and Stacks to Your
Hub
You can connect the PS Hub to different hubs and stacks (for example
a stack of SuperStack II Hub 10 units), giving you flexibility when
creating a new network, or expanding an existing network.
In order to conform with Ethernet rules, you can only have four
repeaters in series. For a stack of more than one PS Hub, any path
through the stack counts as going through two logical repeaters.
Each of the PS Hub’s 10BASE-T ports are internally crossed (MDIX).
The type of cable and ports used must be correct for the connection to
work:
■
You can use ‘Straight-through’ 10BASE-T cable to connect a
crossover (MDIX) port to an uncrossed (MDI) port.
■
You can use ‘Crossover’ 10BASE-T cable to connect two crossover
(MDIX) ports.
The last port (port 12 or 24) on the PS Hub can be either crossed or
uncrossed. The MDI/MDIX switch affects the port’s state:
■
If the switch is IN, the port is uncrossed (MDI).
■
If the switch is OUT, the port is crossed (MDIX).
Figure 3-7 shows a SuperStack II Hub 10 connected to the PS Hub.
A ‘Straight-through’ cable is used, and one of the SuperStack II Hub 10
unit’s crossed (MDIX) ports is connected to port 24 on the PS Hub
(note that the MDI/MDIX switch is IN, so the port is uncrossed).