Making A Connection Via The Mdi Cascade Port; Distance Limit For Fast Ethernet Cabling - HP J4091A Installation And Reference Manual

HP 100Base-T Hub 8 Installation and Reference Guide

Making a Connection via the MDI Cascade Port

1. To make a direct connection to another compatible Class II repeater or
switch, use the 8MDI cascade port. When connecting to this port,
remember not to use port 8MDI-X.
2. Prepare straight-through shielded or unshielded twisted-pair cables with
RJ-45 plugs at both ends. Use 100Ω Category 5 cable for all
connections. Connect one end of the cable to Port 8MDI on this hub,
and the other end to a standard MDI-X port on the other device. When
inserting an RJ-45 plug, be sure the tab on the plug clicks into position
to ensure that it is properly seated.
Notes: 1. When connecting to port 8MDI, do not use port 8MDI-X.
2. Make sure the length of twisted-pair cable does not exceed 100 meters.
3. To connect to another hub or switch, you may also run straight-through
twisted-pair cabling from an MDI-X port on this hub to a cascade port on
another device. However, if you must connect to another hub or switch
via similar port types at both ends of the cable, use crossover cabling.

Distance Limit for Fast Ethernet Cabling

For 100Base-T, network diameter is very important, because each packet
must propagate through the Ethernet collision domain before the next
packet is sent. Every 100Base-T hub (repeater) adds a small propagation
delay to the packet, which can be equated to a certain number of bit times.
The propagation delay (repeater delay) of the HP 100Base-T Hub 8 is 80
bit times, or a cable equivalent length of 72 meters.
The 100Base-T maximum cable distance ("network diameter") is 367
meters. And the maximum distance from a hub to an end-node is 100
meters. To cascade two HP 100Base-T Hub 8s together, we must do this
calculation:
For an end-node on one hub to communicate with an end-node on the other
hub, the cable distance from end-nodes to hubs would be 100m + 100m
(perhaps a bit less, but we should consider the "worst case"). The packets
would traverse through both hubs, for a cable equivalent length of 72m +
72m. This gives:
Installing the System 2-3