Choosing The Correct Cables - 3Com SuperStack 3 3870 Getting Started Manual

Choosing the
Correct Cables
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 Advanced Redundant
Power System output.
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
Switch to Switch
(MDIX to MDIX)
Switch to Hub
(MDIX to MDIX)
Switch to PC (NIC)
(MDIX to MDI)
CAUTION: If you want to install the Switch using a Category 5E or
Category 6 cable, 3Com recommends that you briefly connect the cable
to a grounded port before connecting to the network equipment. If you

Choosing the Correct Cables

Cross-over Cable
✓
✓
✕
Straight-through Cable
✕
✕
✓
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