Information Technology Reference
In-Depth Information
Step 5
Implement the action plan, performing each step carefully while testing to see whether the symptom
disappears.
Step 6
Whenever you change a variable, be sure to gather results. Generally, you should use the same method
of gathering facts that you used in Step 2 (that is, working with the key people affected, in conjunction
with utilizing your diagnostic tools).
Step 7
Analyze the results to determine whether the problem has been resolved. If it has, then the process is
complete.
Step 8
If the problem has not been resolved, you must create an action plan based on the next most likely
problem in your list. Return to Step 4, change one variable at a time, and repeat the process until the
problem is solved.
If you exhaust all the common causes and actions—either those outlined in this topic or
ones that you have identified for your environment—you should contact your Cisco
technical support representative.
Note
Preparing for Network Failure
It is always easier to recover from a network failure if you are prepared ahead of time. Possibly the most
important requirement in any network environment is to have current and accurate information about that
network available to the network support personnel at all times. Only with complete information can
intelligent decisions be made about network change, and only with complete information can
troubleshooting be done as quickly and as easily as possible.
During the process of network troubleshooting, the network is expected to exhibit abnormal behavior.
Therefore, it is always a good practice to set up a maintenance time window for troubleshooting to
minimize any business impact. Always document any changes being made so that it is easier to back out
if troubleshooting has failed to identify the problem within the maintenance window.
To determine whether you are prepared for a network failure, answer the following questions:
Do you have an accurate physical and logical map of your internetwork?
Does your organization or department have an up-to-date internetwork map that outlines the
physical location of all the devices on the network and how they are connected, as well as a logical
map of network addresses, network numbers, subnetworks, and so forth?
•
Do you have a list of all network protocols implemented in your network?
For each of the protocols implemented, do you have a list of the network numbers, subnetworks,
zones, areas, and so on that are associated with them?
•
Do you know which protocols are being routed?
For each routed protocol, do you have correct, up-to-date router configuration?
•
Do you know which protocols are being bridged?
Are any filters configured in any bridges, and do you have a copy of these configurations?
•
Do you know all the points of contact to external networks, including any connections to the
Internet?
For each external network connection, do you know what routing protocol is being used?
•
Do you have an established baseline for your network?
•
