Filter
Top Products
AT-9400 Series Gigabit Ethernet Switches Installation Guide
67
Twisted Pair Port Link LED is Off
When a twisted pair port on the switch is connected to a properly operating
end node, the Link LED for the port should be on. If a Link LED is off, do
the following:
Verify that the end node connected to the port is powered ON and is
operating properly.
Check that the twisted pair cable is securely connected to the port on
the switch and to the port on the end node.
Make sure that the twisted pair cable does not exceed 100m (328 ft).
Verify that you are using the appropriate category of twisted pair cable.
For information, refer to Table 9 on page 48.
Determine if a crossover cable is required. Since the twisted pair ports
feature auto MDI/MDI-X, you should be able to use a straight-through
cable regardless of the type of device you connect to a port. However,
if you disable Auto-Negotiation on a port and set a port’s speed and
duplex mode manually, the port defaults to MDI-X. Disabling Auto-
Negotiation may require manually configuring a port’s MDI/MDI-X
setting or using a crossover cable.
Make sure that the operating parameters of the port on the switch are
compatible with the end node to which the port is connected. This may
require using the switch’s management software.
Note
A 1000Base-T connection can take from five to ten seconds to
establish a link.
If a switch port is using Auto-Negotiation, the default setting, to set its
speed and duplex mode settings, the end node connected to the port
should also be using Auto-Negotiation to prevent a duplex mode
mismatch. This can occur because a switch port that is using Auto-
Negotiation will default to the half-duplex mode if it detects that the end
node is not using Auto-Negotiation. If the end node is operating at a
fixed duplex mode of full-duplex, the result will be a mismatch of
settings on the two devices, with the switch port using half-duplex and
the end node using full-duplex.
To avoid this problem, you should disable Auto-Negotiation on a switch
port and set the port’s speed and duplex mode manually if the end
node has a fixed duplex mode of full-duplex.
The switch has a bad cable detection feature that enables it to
determine if a twisted pair cable has a electrical short that might cause
a network loop. If the switch detects a bad cable on a port, it does not
establish a link on that port. Try replacing the cable.