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Troubleshooting
Basic Troubleshooting Tips
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3-2
Improper Network Topologies. It is important to make sure you have
a valid network topology. Common topology faults include excessive
cable length and excessive repeater delays between end nodes. If you have
network problems after recent changes to the network, change back to
the previous topology. If you no longer experience the problems, the new
topology is probably at fault. Sample topologies are shown at the end of
chapter 2 in this book.
In addition, you should make sure that your network topology contains
no data path loops. Between any two end nodes, there should be only
one active cabling path at any time. Data path loops will cause broadcast
storms that will severely impact your network performance.
If you wish to build redundant paths between important nodes in your
network to provide some fault tolerance, you should enable Spanning
Tree Protocol support on the switch. This ensures that only one of the
redundant paths is active at any time, thus avoiding data path loops.
Spanning Tree can be enabled through the switch console, the web
browser interface, or EliteView.
The switch also supports Trunking, which allows multiple network
cables to be used for a single network connection without causing a data
path loop. See the Management Guide that came with the switch for more
information on Spanning Tree and on Trunking.
Connecting to devices that have a fixed full-duplex configuration.
The SMC6624M switch RJ-45 ports are configured as "Auto." That is, when
connecting to attached devices, the switch will operate in one of two ways
to determine the link speed and the communication mode (half duplex or
full duplex):
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if the connected device is also configured to Auto, the switch will
automatically negotiate both link speed and communication mode
•
if the connected device has a fixed configuration, for example 100
Mbps, at half or full duplex, the switch will automatically sense the
link speed, but will default to a communication of half duplex
Because the SMC6624M switch behaves in this way (in compliance with
the IEEE 802.3 standard), if a device connected to the switch has a fixed
configuration at full duplex, the device will not connect correctly to the
switch. The result will be high error rates and very inefficient communi-
cations between the switch and the device.
Make sure that all devices connected to the SMC6624M switch are config-
ured to auto negotiate, or are configured to connect at half duplex (all
hubs are configured this way, for example).
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