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26 CHAPTER 2: INSTALLING THE SWITCH
For full redundancy, the unit requires two Type 3 Power Modules
combined using a Type 3 Y-Cable (part number 3C16077).
WARNING: If you are connecting the Switch to a Type 3 Power Module,
read the Safety Information section in the Type 3 Power Module User
Guide.
CAUTION: The Switch can only use a SuperStack Advance Redundant
Power System output.
Choosing the Correct
Cables
All of the ports on the Switch are Auto-MDIX, that is they have a
cross-over capability. These ports can automatically detect whether to
operate in MDI or MDIX mode. Therefore you can make a connection to
one of the ports with a straight-through (MDI) or a cross-over cable
(MDIX).
The Auto-MDIX feature only operates when auto-negotiation is enabled.
If auto-negotiation is disabled, all the Switch ports are configured as
MDIX (cross-over). If you want to make a connection to another MDIX
port, you need a cross-over cable. Many ports on workstations and
servers are configured as MDI (straight-through). If you want to make a
connection to an MDI port, you need to use a standard straight-through
cable. See Table 8
.
3Com recommends that you use at least Category 5 twisted pair cable —
the maximum segment length for this type of cable is 100 m (328 ft.).
Table 8 Cables required to connect the Switch to other devices if
auto-negotiation is disabled
Cross-over Cable Straight-through Cable
Switch to Switch
(MDIX to MDIX)
✓ ✕
Switch to Hub
(MDIX to MDIX)
✓ ✕
Switch to PC (NIC)
(MDIX to MDI)
✕ ✓
DUA1745-0AAA02.book Page 26 Monday, August 9, 2004 11:51 AM