HP J2415A Installation And Reference Manual page 75

Hub Reference
RJ-45 100VG LAN Ports
The Hub-14 has 12 twisted-pair LAN ports to connect network devices, such
as end node PCs, servers or other hubs. The LAN ports consist of built-in
(8-pin) jacks for use with twisted-pair cables. Each LAN port requires four
twisted-pair wires (8 wires total). Each LAN cable can be unbundled or
bundled as described on page 1-16.
The hub can operate in a "store-and-forward" mode when transmitting
broadcast and multicast packets to minimize crosstalk on bundled cable
(cable with 25 or more twisted-pairs). Store-and-forwarding allows
group-addressed packets to be transmitted to all ports by storing the packet
as the end node transmits it, and then re transmitting the packet once
reception from the end node is complete. This prevents the simultaneous
transmission and receptions of packet signals on bundled cable that can
cause crosstalk interference.
If you presently have a four-pair, twisted-pair cable network that complies
with the Ethernet/IEEE 802.3 standard, you can use the same cables on a
100VG network.
For more information on supported LAN port cables, see the
HP 100VG-AnyLAN Technology Guide and refer to appendix A.
100VG Modular Slots
The Hub-14 has two modular LAN ports to connect to other 100VG hubs or
end nodes. Each modular port accepts an optional transceiver such as the
HP J3028A 100VG Twisted-Pair Transceiver Module or HP J3030A 100VG
Fiber-Optic Multimode ST Transceiver Module. (Other transceivers may be
available. Contact your HP-authorized dealer for more information.) You
can use these ports as uplink ports or use port 12B as a downlink port. (Be
sure to read the section titled Optional Downlink Port (12B) on the next
page for more information.)
Redundant Uplink Slots By default, these slots are for cascading hubs
together on a 100VG network. In these slots you can install the optional
100VG transceivers listed above.
Redundant means that one uplink is a backup of the other. If one link were
to fail, the other link will take over. Only one of the uplink connections will
be active and transfer data at any given time. An Uplink port on a
lower-level hub connects to any of the LAN downlink ports on an upper-level
hub using appropriate cable for a 100VG connection. For additional LAN
cable information, refer to appendix A.
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