Port Connection Problems
Port connection problems can usually be traced to a poor cable connection or to an improper connection of the port cables at either end of the link. These types of problems can be remedied by making sure that the cable connections are secure and that the cables are connected to the correct ports at both ends of the link.
For more information about cabling, see “Cabling,” next in this chapter.
Port connection problems can also be traced to the autonegotiation mode (refer to “Autonegotiation Modes” on page 4-5) or the port interface.
Cabling
Cabling for 10BASE-T networks can consist of 2-pair Category 3, 4, or 5 unshielded twisted pair (UTP) wiring. However, to cover future upgrades to Fast Ethernet, Nortel Networks strongly recommends that you use all Category 5 cable in your network.
Ethernet 10BASE-T network installations use cables consisting of two pairs of twisted pair wires—one pair to send data and one to receive data. These wires must connect to another 10BASE-T station that has the sending pair attached to its receiving pair and vice versa. In this way, the two nodes can exchange data. If the two nodes are wired alike, they both attempt to send data out on the same RJ-45 pins. In such a case, a straight-through cable would not work. However, a crossover cable would operate normally.
The Passport 8100 Series modules are designed to have Ethernet NICs connect directly to their RJ-45 ports using straight-through (MDI) cables. However, if a Passport 8100 module must connect to a hub or another switch that follows usual conventions, a crossover cable (MDI-X) is required.
The 100 Mb/s ports are designed to operate using Category 5 UTP cabling only. Category 5 UTP cable is a 2-pair cable certified to handle up to 100 Mb/s bandwidth. To minimize crosstalk noise, maintain the twist ratio of the cable up to the point of termination; untwist at any termination should not exceed 0.5 inch (1.27 cm).
For best performance with respect to noise immunity and emissions, the unused pairs in the 2-pair cable should be terminated at their characteristic impedance (that is, 100 ohms) in the equipment at each end of the cable. All Nortel Networks 100BASE-TX equipment includes such a Common Mode Termination (CMT).
