The general purpose of a
network configuration table
is to give a listing of the hardware and
software components used in the network. This information will be used in the course of troubleshooting
to ensure that the functioning of the network is well understood. At a minimum, a
network configuration table should include the name of the network device, the layer 2 addresses
and implemented feature sets, and the layer 3 addresses and implemented features. In addition
to these items, you should include any additional information about layers 4 through 7 that is
deemed important (for instance, extended access lists and application flow details). Finally, all of
the specifics about the physical devices should be recorded (their location in the computer room,
their UPS circuit information, and so forth).
One of the most common ways to determine the specific items that will go into your network
configuration table is to divide the types of information being observed into groups corresponding
to the layers of the OSI model. Some items, such as name of the device, do not necessarily
fall in a particular layer, but these can be incorporated as part of the Physical layer or placed in
a separate column. A sample list of items that can be included in a network configuration table
is shown in Table 34.1.
Sample List of Network Configuration Table Items
Classification Items
Miscellaneous Information Device name, device model, CPU type, flash memory,
DRAM, interface description
Layer 1 Media type, speed, interface numbers, connecting jack
or port
Layer 2 MAC address, Spanning Tree Protocol (STP) state, STP root
bridge, portfast information, VLAN(s), EtherChannel configuration,
encapsulation, trunking status, interface type,
port security, VTP state, VTP mode
Layer 3 IP address, IPX address, secondary IP address, Hot Standby
Routing Protocol (HSRP) address, subnet, subnet mask,
routing protocol(s), access lists, tunneling information,
loopback interfaces
Cisco technically considers the list of items under miscellaneous information
as layer 1 items.
Once you have identified the information that you will put in your network configuration
table, the next step is organizing this information in a logical and repeatable sequence. When
planning the organization of this information, you must take into account all the device types
that are in the network as well as the needs of each of these devices. Due to the variation in the
requirements for different types of network devices such as switches and routers, in many cases
you will need a different table structure for each major classification of device. For example, in
most instances, there will be one set of information gathered for routers and a separate set of
information for switches. This separation prevents a lot of unnecessary fields that are left empty
because they do not apply. By separating these information groups, you can simplify the overall
network documentation.
If you do decide to separate switches from routers in your network documentation,
be sure to have a plan for how to account for devices that do
both
routing
and switching. You might create both a routing and a switching document
for such devices. Alternately, you could create a third set of documentation
specifically for these types of devices.
In most cases, the preferred manner to store this information is in a spreadsheet or database.
For smaller networks, a spreadsheet is usually the preferred method due to its low cost and ease
of use. For large networks, a database is the preferred arrangement because of its flexibility, and
it lets you better manage large volumes of data. For both of these means of storage, hard copies
of the information should be maintained in addition to the electronic versions. This paper documentation
may be critical during a network outage, when the information contained in the network
configuration table will be most useful and you may not be able to access the online version.