3Com 1000 - Manual (Page 10)

1-2 C HAPTER 1: G ETTING S TARTED
Port Connections
10BASE-T Ports
The Switch has 12 or 24 10BASE-T ports config-
ured as MDIX (cross-over), which provide a full
10Mbps bandwidth to attached endstations. Maxi-
mum segment length is 100m (328ft) over grade 3,
4, or 5 twisted pair cable.
As these ports are configured as MDIX (cross-over),
you need to use a cross-over cable to connect to
devices whose ports are MDIX-only. Most of the
10BASE-T ports in 3Com devices are MDIX-only.
100BASE-TX Port
The Switch has a single Fast Ethernet 100BASE-TX
port configured as MDIX (cross-over), which provides
a 100Mbps connection to, for example, a local
server. The maximum segment length is 100m
(328ft) over grade 5 twisted pair cable.
As this port is configured as MDIX (cross-over), you
need to use a cross-over cable to connect to devices
whose ports are MDIX-only. Most of the
100BASE-TX ports in 3Com devices are MDIX-only.
Plug-in Module
A slot at the rear of the unit can take a Plug-in
Module, providing an additional high-speed port.
This could be used, for example, to provide a Fast
Ethernet or Asynchronous Transfer Mode (ATM)
backbone connection to the rest of your network.
Transceiver Module
A slot at the rear of the unit allows you to install
any of the 3Com 10Mbps Ethernet Transceiver Mod-
ules. When a Transceiver Module is fitted, port 1
automatically switches to become the Transceiver
Module port. The Transceiver Module can provide a
10Mbps link to the rest of your network.
Backbone Port
The Switch allows you to specify any port to be a
backbone port with the following attributes:
■ Frames with unknown addresses received by the
Switch are forwarded to the port.
■ Addresses received on the port are not stored in
the Switch Database (the database which con-
tains the device addresses received by the
Switch).
A backbone port is typically used to connect the
Switch to the backbone of large networks (over 500
MAC addresses). For information about how to
specify a backbone port for a new or initialized
Switch, refer to
“Setting Up the Switch Unit” on
page 4-9 .
You can specify one backbone port for each VLAN
defined on the Switch. For more information about
how to specify a backbone port for a VLAN, refer to
“Setting Up VLANs on the Switch” on page 5-8 .