As we learned in the previous chapter, a well documented and well maintained network is a lot easier to support and troubleshoot than one with little or no documentation and is not regularly maintained. In other words, a structured maintenance approach facilitates or simplifies the troubleshooting and support functions of overall network management. In essence, effective troubleshooting is dependent on the tasks and tools that are part of the structured maintenance process. This section describes the ways maintenance facilitates the troubleshooting process.
Establishing a Baseline
Baselining is a process for studying the network, including devices that constitute the network, at regular intervals. A baseline is more than just a single randomly run report detailing the health of the network at any given point in time, it is a continual process. Baselining facilitates the troubleshooting process by allowing troubleshooters to differentiate between normal and abnormal behavior when troubleshooting problem reports. By following the baseline process, you can perform the following:
- Get information on the health of the hardware and software
- Predict future problems
- Determine the current utilization of network resources
- Identify current network problems
- Make accurate decisions about network alarm thresholds
The baselining process can be used to determine the network break point, which is the point at which the network will break. The network break point can be determined through the knowledge of how the hardware and software in the network perform. This information can be used to identify and properly plan for critical resource limitation issues in the network, i.e. capacity planning. Several tools can be used to establish a baseline, including, but not limited to Cisco IP SLA operations, SNMP, Cisco IOS NetFlow and CiscoWorks LMS.
Documentation
Documentation, a core maintenance function, is integral to the troubleshooting process. As was stated in chapter 1, it is important to ensure that the network is well documented and that the documentation is accurate and well maintained. Attempting to troubleshoot a network using incorrect documentation is oftentimes worse than attempting to troubleshoot a network without any documentation at all. As was also stated in chapter 1, good documentation should include the following information about the network:
- Information about the interconnects between devices for LAN and WAN connections
- IP addressing and VLAN information
- A physical topology diagram of the network
- A logical topology diagram of the network
- An inventory of all internetwork devices, components and modules
- A revision control section detailing changes to the topology
- Configuration information
- Any original or additional design documentation and notes
- Data or traffic flow patterns
The maintenance of network documentation and configuration can be facilitated by using some of the tools described in chapter 1. Examples of tools that can be used to facilitate the documentation maintenance function include the Embedded Event Manager (EEM), the Configuration Archive and Rollback feature, as well as the Configuration Scheduler (KRON).
Change Management
Change management or change control is an integral component of the network maintenance process. The objective of the change management process is to minimize network and service downtime by ensuring that requests for changes are recorded and then evaluated, authorized, prioritized, planned, tested, implemented, documented and reviewed in a controlled and consistent manner. A change can involve any configuration item or element of infrastructure. Some examples of changes include the following:
- Environmental changes
- Network changes
- Application changes
- Hardware changes
- Documentation changes
- Software changes
Ensuring that changes to network devices are performed in a controlled, well documented manner reduces the likelihood of unplanned network outages. Troubleshooting is also simplified when changes are performed in a controlled environment. The change control process also ensures that network documentation is also updated following the change.