24CHAPTER 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 All of the ports on the Switch are Auto-MDIX, that is they have a Cables 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-overcable. 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-throughcable. 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)

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3Com 3CR17450-91, 3CR17451-91 manual Power System output, Cross-over Cable Straight-through Cable