AT-30xxSL Multiport Repeaters
21
UTP MAU-to-MAU,
Hub-to-Hub Wiring
10Base-T MAU-to-MAU or hub-to-hub wiring generally requires a crossover
cable located somewhere along the UTP cable run. This may commonly occur
at the punch-down block or between the RJ-45 wall connector and the
workstation. See Figure 15.
Figure 15: Hub-to-Hub or MAU-to-MAU Wiring
MDI/MDI-X Switch
The MDI/MDI-X pin-out switch affects the RJ-45 Port 1. The RJ-45 pin-out
straight-through (MDI)/crossover (MDI-X) switch enables you to use a
straight-through cable (Figure 14) during hub-to-hub connectivity by simply
placing the switch in the MDI position. This eliminates the need for making or
obtaining a crossover cable.
The interface type that IEEE specifies as a standard for these repeaters is the
MDI-X switch. The straight-through/crossover switch merely provides
convenience in having to obtain an alternate cable in some applications. If you
connect a cable and it does not work, try changing the MDI switch. The rule of
thumb is the total number of crossovers must be odd. You cannot harm the
repeater by having the MDI switch in the wrong position.
Table 3 shows the required positions for the straight-through/crossover
selection switch dependent on the configuration. Table 3 assumes a straight-
through cable is being used for all three models. The switch setting are the
opposite of what is shown if a crossover cable is being used.
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
RJ 45 Pin
RJ 45 Pin
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Pair twisted as per level 3, 4 or 5 cable
1
1
1
Table 3: MDI and MDI-X Switch Settings for Common Connection
Connected to
MDI
MDI-X
Hub
X
RJ-45 Transceiver
X
NIC
X
