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Understanding Maintenance Methods
Network maintenance is an inherent component of a network administrator’s responsibilities.
However, that network administrator might be performing maintenance tasks in response
to a reported problem. This reactive approach is unavoidable, because unforeseen
issues do arise. However, the occurrence of these interrupt-driven maintenance tasks can
be reduced by proactively performing regularly scheduled maintenance tasks.
You could think of regularly scheduled tasks, such as performing backups and software
upgrades, as important but not urgent. Spending more time on the important tasks can
help reduce time spent on the urgent tasks (for example, responding to user connectivity
issues or troubleshooting a network outage).
This section begins by identifying several network maintenance tasks. Common network
maintenance models are discussed. However, an off-the-shelf network maintenance model
might not be a perfect fit for your organization. So, this section concludes by discussing
how a well-known model can be adapted to your needs.
Introducing Network Maintenance
Before discussing approaches to network maintenance, let us first spend a few moments
defining network maintenance. Network maintenance, at its essence, is doing whatever is required
to keep the network functioning and meeting the business needs of an organization.
Some examples of the tasks that fall under the umbrella of network maintenance are as
follows:
■ Hardware and software installation and configuration
■ Troubleshooting problem reports
■ Monitoring and tuning network performance
■ Planning for network expansion
■ Documenting the network and any changes made to the network
■ Ensuring compliance with legal regulations and corporate policies
■ Securing the network against internal and external threats
Obviously, this listing is only a sampling of network maintenance tasks. Also, keep in
mind that the list of tasks required to maintain your network could be quite different from
the list of tasks required to maintain another network.
Proactive Versus Reactive Network Maintenance
Network maintenance tasks can be categorized as one of the following:
■ Structured tasks: Performed as a predefined plan.
■ Interrupt-driven tasks: Involve resolving issues as they are reported.
As previously mentioned, interrupt-driven tasks can never be completely eliminated; however,
their occurrence can be lessened through a strategic structured approach.
Not only does a structured maintenance approach offer reduced downtime (by fixing
problems before they occur), it also proves to be more cost effective. Specifically, unplanned
network outages can be resolved more quickly. Fewer resources are consumed
responding to problems, because fewer problems occur. Also, because a structured
maintenance approach includes planning for future network capacity, appropriate hardware
and software purchases can be made early on, reducing obsolescence of relatively
new purchases.
Because a structured approach considers underlying business goals, resources can be allocated
that complement business drivers. Also, security vulnerabilities are more likely to be
discovered through ongoing network monitoring, which is another component of a structured
maintenance approach.
Well-Known Network Maintenance Models
The subtleties of each network should be considered when constructing a structured network
maintenance model. However, rather than starting from scratch, you might want to
base your maintenance model on one of the well-known maintenance models and make
adjustments as appropriate.
The following is a sampling of some of the more well-known maintenance models:
■ FCAPS: FCAPS (which stands for Fault management, Configuration management,
Accounting management, Performance management, and Security management) is a
network maintenance model defined by the International Organization for Standardization
(ISO).
■ ITIL: An IT Infrastructure Library (ITIL) defines a collection of best-practice recommendations
that work together to meet business goals.
■ TMN: The Telecommunications Management Network (TMN) network management
model is the Telecommunications Standardization Sector’s (ITU-T) variation of the
FCAPS model. Specifically, TMN targets the management of telecommunications
networks.
■ Cisco Lifecycle Services: The Cisco Lifecycle Services maintenance model defines
distinct phases in the life of a Cisco technology in a network. These phases are
Prepare, Plan, Design, Implement, Operate, and Optimize. As a result, the Cisco
Lifecycle Services model is often referred to as the PPDIOO model.
Adapting a Well-Known Network Maintenance Model
The maintenance model you use in your network should reflect business drivers, resources,
and expertise unique to your network. Your maintenance model might, however,
be based on one of the previously discussed well-known maintenance models.
8 CCNP TSHOOT 642-832 Official Certification Guide
Table 1-2 FCAPS Management Tasks
Type of Management Examples of Management Tasks
Fault management Use network management software to collect information from
routers and switches. Send an e-mail alert when processor utilization
or bandwidth utilization exceeds a threshold of 80 percent.
Respond to incoming trouble tickets from the help desk.
Configuration management Require logging of any changes made to network hardware or
software configurations. Implement a change management system
to alert relevant personnel of planned network changes.
Accounting management Invoice IP telephony users for their long distance and international
calls.
Performance management Monitor network performance metrics for both LAN and WAN
links. Deploy appropriate quality of service (QoS) solutions to
make the most efficient use of relatively limited WAN bandwidth,
while prioritizing mission critical traffic.
Security management Deploy firewall, virtual private network (VPN), and intrusion
prevention system (IPS) technologies to defend against malicious
traffic. Create a security policy dictating rules of acceptable
network use. Use an Authorization, Authentication, and
Accounting (AAA) server to validate user credentials, assign
appropriate user privileges, and log user activity.
Chapter 1: Introduction to Network Maintenance 9
As an example, imagine you have selected the ISO FCAPS model as the foundation for
your maintenance model. To adapt the FCAPS model for your environment, for each element
of the FCAPS model, you should identify specific tasks to perform on your network.
Table 1-2 provides a sampling of tasks that might be categorized under each of the FCAPS
management areas.
By clearly articulating not just a theoretical methodology but actionable and measurable
processes, you can reduce network downtime and more effectively perform interruptdriven
tasks. This structured approach to network management helps define what tools are
needed in a toolkit prior to events requiring the use of those tools.
Identifying Common Maintenance Procedures
Although the listings of procedures contained in various network maintenance models
vary, some procedures are common to nearly all network maintenance models. This section
identifies common network maintenance tasks, discusses the importance of regularly
scheduled maintenance, and summarizes critical network maintenance areas.
Routine Maintenance Tasks
Some routine maintenance tasks should be present in a listing of procedures contained in a
network maintenance model. Following is a listing of such common maintenance tasks:
■ Configuration changes: Businesses are dynamic environments, where relocation of
users from one office space to another, the addition of temporary staffers, and new
hires are commonplace. In response to organizational changes, network administrators
need to respond by performing appropriate reconfigurations and additions to
network hardware and software. These processes are often referred to as moves, adds,
and changes.
■ Replacement of older or failed hardware: As devices age, their reliability and
comparable performance tend to deteriorate. Therefore, a common task is the replacement
of older hardware, typically with better performing and more feature-rich devices.
Occasionally, production devices fail, thus requiring immediate replacement.
■ Scheduled backups: Recovery from a major system failure can occur much quicker
if network data and device configurations have been regularly backed up. Therefore,
a common network maintenance task is to schedule, monitor, and verify backups of
selected data and configuration information. These backups can also be useful in recovering
important data that were deleted.
■ Updating software: Updates to operating system software (for servers, clients, and
even network devices) are periodically released. The updates often address performance
issues and security vulnerabilities. New features are also commonly offered in
software upgrades. Therefore, performing routine software updates becomes a key
network maintenance task.
■ Monitoring network performance: The collection and interpretation of traffic statistics,
bandwidth utilization statistics, and resource utilization statistics for network
devices are common goals of network monitoring. Through effective network monitoring
(which might involve the collection and examination of log files or the implementation
of a high-end network management server), you can better plan for future
expansion (that is, capacity planning), anticipate potential issues before they arise,
and better understand the nature of the traffic flowing through your network.
Benefits of Scheduled Maintenance
After defining the network maintenance tasks for your network, those tasks can be ranked
in order of priority. Some task will undoubtedly be urgent in nature and need a quick response
(for example, replacing a failed router that connects a business to the Internet).
Other tasks can be scheduled. For example, you might schedule weekly full backups of
your network’s file servers, and you might have a monthly maintenance window, during
which time you apply software patches.
By having such a schedule for routine maintenance tasks, network administrators are less
likely to forget an important task, because they were busy responding to urgent tasks.
Also, users can be made aware of when various network services will be unavailable, due
to maintenance windows, thus minimizing the impact on workflow.
Managing Network Changes
Making changes to a network often has the side effect of impacting the productivity of
users relying on network resources. Additionally, a change to one network component
might create a problem for another network component. For example, perhaps a firewall
was installed to provide better security for a server farm. However, in addition to common
protocols that were allowed to pass through the firewall (for example, DNS, SMTP, POP3,
HTTP, HTTPS, and IMAP), one of the servers in the server farm acted as an FTP server,
and the firewall configuration did not consider that server. Therefore, the installation of a
firewall to better secure a server farm resulted in a troubleshooting issue, where users
could no longer reach their FTP server.
The timing of network changes should also be considered. Rather than taking a router
down in order to upgrade its version of Cisco IOS during regular business hours, such an
operation should probably be performed during off hours.
Making different organization areas aware of upcoming maintenance operations can also
aid in reducing unforeseen problems associated with routine maintenance. For example,
imagine that one information technology (IT) department within an organization is responsible
for maintaining WAN connections that interconnect various corporate offices,
whereas another IT department is charged with performing network backups. If the WAN
IT department plans to upgrade the WAN link between a couple of offices at 2:00 AM
next Tuesday, the IT department in charge of backups should be made aware of that
planned upgrade, because a backup of remote data (that is, data accessible over the WAN
link to be upgraded) might be scheduled for that same time period.
Some organizations have a formalized change management process, where one department
announces online their intention to perform a particular maintenance task during a specified
time period. Other departments are then notified of this upcoming change, and determine
if the planned change will conflict with that department’s operations. If a conflict is
identified, the departments can work together to accommodate one another’s needs.
Of course, some network maintenance tasks are urgent (for example, a widespread network
outage). Those tasks need timely response, without going through a formalized change
management notification process and allowing time for other departments to respond.
When defining a change management system for your organization, consider the following:
■ Who is responsible for authorizing various types of network changes?
■ Which tasks should only be performed during scheduled maintenance windows?
■ What procedures should be followed prior to making a change (for example, backing
up a router’s configuration prior to installing a new module in the router)?
■ What measureable criteria determine the success or failure of a network change?
■ How will a network change be documented, and who is responsible for the
documentation?
■ How will a rollback plan be created, such that a configuration can be restored to its
previous state if the changes resulted in unexpected problems?
■ Under what circumstances can formalized change management policies be overridden,
and what (if any) authorization is required for an override?
Maintaining Network Documentation
Network documentation typically gets created as part of a network’s initial design and installation.
However, keeping that documentation current, reflecting all changes made since
the network’s installation, should be part of any network maintenance model. Keeping
documentation current helps more effectively isolate problems when troubleshooting.
Additionally, accurate documentation can prove to be valuable to designers who want
to scale the network.
At a basic level, network documentation could consist of physical and logical network diagrams,
in addition to a listing of network components and their configurations. However,
network documentation can be much more detailed, including such components as formalized
change management procedures, a listing of contact information (for example, for
service providers and points of contact in an organization’s various IT groups), and the
rationale for each network change made.
While the specific components in a set of network documentation can vary, just as the
procedures in a network maintenance model vary, the following list outlines common elements
found in a set of network documentation:
■ Logical topology diagram: A logical topology diagram shows the interconnection
of network segments, the protocols used, and how end users interface with the network.
However, this diagram is not concerned with the physical locations of network
components.
■ Physical topology diagram: Unlike a logical topology diagram, a physical topology
diagram shows how different geographical areas (for example, floors within a
building, buildings, or entire sites) interconnect. The diagram reflects where various
network components are physically located.
■ Listing of interconnections: A listing of interconnections could be, for example, a
spreadsheet that lists which ports on which devices are used to interconnect network
components, or connect out to service provider networks. Circuit IDs for service
provider circuits might be included in this documentation.
■ Inventory of network equipment: An inventory of network equipment would include
such information as the equipment’s manufacturer, model number, version of
software, information about the licensing of the software, serial number, and an organization’s
asset tag number.
■ IP address assignments: An organization might use private IP address space internally
and use network address translation (NAT) to translate those private IP address
space numbers into publicly routable IP addresses. Alternately, an organization might
have public IP addresses assigned to some or all of their internal devices. A classful IP
address space (either public or private) might be subdivided within an organization,
resulting in subnets with a non-default subnet mask. These types of IP addressing
specifications would be included in a set of network documentation.
■ Configuration information: When a configuration change is made, the current configuration
should be backed up. With a copy of current configuration information, a
device could be replaced quicker, in the event of an outage. Beyond having a backup
of current configuration information, some network administrators also maintain
archival copies of previous configurations. These older configurations could prove to
be useful when attempting to roll back to a previous configuration state or when trying
to duplicate a previous configuration in a new location. It is a good practice to
name archival copies of previous configurations based on a certain format that makes
sense to you. For example, some companies name their archival copies by date, others
by function, and still others by a combination of both.
■ Original design documents: Documents created during the initial design of a network
might provide insight into why certain design decisions were made, and how the
original designers envisioned future network expansion.
Larger network environments often benefit from having step-by-step guidelines for troubleshooting
a given network issue. Such a structured approach to troubleshooting helps
ensure that all troubleshooting personnel use a common approach. Although a network issue
might be successfully resolved through various means, if different personnel troubleshoot
using different approaches, at some point those approaches might conflict with
one another, resulting in further issues.
For example, consider one network administrator that configures IEEE 802.1Q trunking
on Cisco Catalyst switches by disabling Dynamic Trunk Protocol (DTP) frames and forcing
a port to act as a trunk port. Another network administrator within the same company
configures 802.1Q trunking by setting a port’s trunk state to desirable, which creates a
trunk connection only if it receives a DTP frame from the far end of the connection.
These two approaches are not compatible, and if each of these two network administrators
configured different ends of what they intended to be an 802.1Q trunk, the trunk
connection would never come up. This example illustrates the criticality of having clear
communication among IT personnel and a set of standardized procedures to ensure consistency
in network configuration and troubleshooting practices.
Restoring Operation After Failure
Although most modern network hardware is very reliable, failures do occur from time to
time. Aside from hardware failures, environmental factors could cause a network outage.
As a few examples, the failure of an air conditioner unit could cause network equipment
to overheat; water leakage due to flooding or plumbing issues could cause hardware failures;
or a fire could render the network equipment unusable.
Planning and provisioning hardware and software for such outages before they occur can
accelerate recovery time. To efficiently replace a failed (or damaged) device, you should be
in possession of the following:
■ Duplicate hardware
■ Operating system and application software (along with any applicable licensing) for
the device
■ Backup of device configuration information
Measuring Network Performance
Network monitoring is a proactive approach to network maintenance, enabling you to be
alerted to trends and utilization statistics (as a couple of examples), which can forecast future
issues. Also, if you work for a service provider, network performance monitoring can
ensure that you are providing an appropriate service level to a customer. Conversely, if you
are a customer of a service provider, network monitoring can confirm that the service
provider is conforming to the SLA for which you are paying.
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