Logical Connections; Device Configuration Information; Other Important Data About Your Network; Normal Behavior On Your Network - Nortel BCM50 Troubleshooting Manual

16 Chapter 2 Initial Troubleshooting

Logical connections

With virtual LANs (VLANs), you must know how your devices are connected logically as well as
physically.

Device configuration information

You should maintain online and paper copies of your device configuration information. Ensure
that all online data is stored with your site's regular data backup. If your site does not have a
backup system, copy the information onto a backup disk (such as a CD or zip disk) and store the
backup disk at an offsite location.

Other important data about your network

For a complete picture of your network, have the following information available:
• All passwords—Store passwords in a safe place. It is a good practice to keep records of your
previous passwords in case you must restore a device to a previous software version and need
to use the old password that was valid for that version.
• Device inventory—It is a good practice to maintain a device inventory, which list all devices
and relevant information for your network. The inventory allows you to easily see the device
type, IP address, ports, MAC addresses, and attached devices.
• MAC address-to-port number list—If your hubs or switches are not managed, you must
keep a list of the MAC addresses that correlate to the ports on your hubs and switches.
• Change control—Maintain a change control system for all critical systems. Permanently store
change control records.
• Contact details—It is a good practice to store the details of all support contracts, support
numbers, engineer details, and telephone and fax numbers. Having this information available
when troubleshooting can save a lot to time.

Normal behavior on your network

When you are familiar with the performance of your network when it is fully operational, you can
be more effective at troubleshooting problems that arise. To understand the normal behavior of
you network, monitor your network over a long period of time. During this time you can see a
pattern in the traffic flow, such as which devices are typically accessed or when peak usage times
occur.
To identify problems, you can use a baseline analysis, which is an important indicator of overall
network health. A baseline serves as a useful reference of network traffic during normal operation,
which you can then compare to captured network traffic while you troubleshoot network
problems. A baseline analysis speeds the process of isolating network problems. By running tests
on a healthy network, you compile normal data for your network. This normal data can then be
used to compare against the results that you get when your network is experiencing trouble. For
example, ping each node to discover how long it typically takes to receive a response from devices
on your network. Capture and save each device's response time and when you are troubleshooting
you can use these baseline response times to help you troubleshoot.
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