General Approach to Troubleshooting
Preparing for network failure

It is always easier to recover from a network failure when preparations are made ahead of time. Possibly the most important requirement in any network environment is to have current and accurate information about the network available to the network support personnel at all times. Complete information is necessary to allow for intelligent decisions related to network change. Complete information also allows troubleshooting to be performed as quickly and easily as possible. During the process of troubleshooting the network, it is most important to ensure that this documentation is kept up-to-date.

To help prepare for a network failure, answer the following questions:

  • Is there an accurate physical and logical map of the network?
    • Does the organization or department have an up-to-date network map that outlines the physical location of all the devices on the network and how they are connected?
    • Does it have a logical map of network addresses, network numbers, subnetworks, and so forth?
  • Is there an established baseline for the network?
    • Has the organization documented normal network behavior and performance at different times of the day?
  • Is there a list of all network protocols implemented in the network?
    • For each of the protocols implemented, is there a list of the network numbers, subnetworks, zones, areas, and so on that are associated with them?
  • Which protocols are being routed ?
    • For each routed protocol, is there a correct, up-to-date router configuration?
  • Which protocols are being bridged?
    • Are there any filters configured in any bridges? If so, is there a copy of these configurations?
  • What are the points of contact to external networks, including any connections to the Internet?
    • For each external network connection, what routing protocol is being used ?