Network topology diagrams Note
that it is now common practice to compile network documentation
on a website.
Content 1.2 Network Configuration
Documentation 1.2.2 Identifying the components
of a network configuration table A network configuration
table contains accurate, up-to-date records of the hardware and
software used in a network. The network configuration table
should provide the troubleshooter with all the information
necessary to identify and correct the network fault. When a
network configuration table is created for troubleshooting, the
contents will vary depending upon the type of device that is
documented. A minimum amount of data should be included for all
components: - The type of device, model designation
- The device network hostname
- The location of
the device (building, floor, room, rack, panel)
- If it
is a modular device, include all the module types and in which
module slot they are located
- Data link layer
addresses
- Network layer addresses
- Any
additional important information about physical aspects of the
device
Due to the complex nature of most networks,
there is a great deal of information that could be recorded.
For simplicity and efficiency, network configuration tables
should group information based on the layers of the OSI
networking model. Network documentation will vary depending on
the purpose of the documentation and the types of devices that
are being documented. A configuration table constructed for
budgetary purposes might include serial number, date of
purchase, cost, vendor, and warranty expiration date. These
items would not benefit a troubleshooter and should be
maintained in separate tables. Configuration table contents
will also vary depending on the features implemented on the
devices. The Router ID is an important piece of information to
record about a router running OSPF. However, the Router ID
would not be recorded if only EIGRP was running. Figure
displays an example of a network configuration table for a
router. Figure documents an example of a network configuration
table for a switch.
Content 1.2 Network
Configuration Documentation 1.2.3 Identifying
the components of a topology diagram A topology diagram is
a graphical representation of a network. A topology diagram
illustrates how each device in a network is connected, while
also detailing the aspects of its logical architecture.
Topology diagrams share many of the same components as their
network configuration table counterparts. Each network device
should be represented on the diagram with consistent notation
or a graphical symbol. Also, each logical and physical
connection should be represented using a simple line or some
other appropriate symbol. At a minimum, most topology diagrams
include illustrations of all devices and how they are
connected. Many topologies also include network cloud symbols.
A labeled cloud symbol is often employed to represent entities
that are either outside the autonomous control of the network
or outside the scope of the topology diagram. The cloud symbols
are placeholders signifying that a network, or collection of
networks, exists. It is not particularly relevant to the
diagram to know anything specifically about those networks.
Although the components of a topology diagram can be restricted
to a particular layer of the TCP/IP model, most often they are
a combination of the most important components of several
logical layers. To illustrate the important components at the
network layer of the TCP/IP layer, IP addresses, subnet masks,
and routing protocols might be included. Some topologies are
informal hand-drawn sketches, while others are more elaborate,
using detailed symbols, multiple colors, and different ways to
view them. The latter are typically created using graphics
applications that vary in functionality. While some
applications can be used as a solution to manually create a
network diagram, others can automatically create and maintain a
topology of an existing network. Figure is an example of a
topology diagram including the device name, interface name, IP
address, and routing protocols. Figure is an example of a
topology diagram including the device name, interface name, and
IP address.
Content 1.2 Network Configuration
Documentation 1.2.4 Discovering network
configuration information The following steps outline the
procedure for discovering the network configuration of a router
or multilayer switch. Step 1
View the name and model
of the device, as well as the version of operating system that
the device is running.
• Enter show
version. Step 2
Determine active interfaces and
their addresses.
• Enter show ip interfaces.
Step 3
View a brief summary of the interfaces on the
device including the IP address, interface name, media type,
status of the configuration, and physical and data link
operational status.
• Enter show ip interfaces
brief. Step 4
View the MAC address for any
interface or port.
• Enter show ip interface
{interface-name} for each interface or enter
show interfaces to see a list of all interfaces at once.
Step 5
View a summary of both the IP and non-IP
routing protocols enabled for the device.
• Enter
show ip protocols. Step 6
View details about
the spanning tree status on the device.
• Depending
on the IOS version, enter show spanning-tree or show
spantree. Step 7
View a list of directly
connected Cisco devices.
• Enter show cdp
neighbors. Step 8
View details about any
connected devices such as IP address and capabilities.
• Enter show cdp entry {device id}. The
following steps outline the procedure for discovering the
network configuration of a Layer 2 switch. Step 1
View the name and model of the device, as well as the version
of operating system that the device is running.
•
Enter show version. Step 2
Determine
active ports and their addresses.
• Enter show
interfaces description. Step 3
View a summary of
the ports on the device including port names, port status,
duplex, and speed.
• Enter show interfaces
status. Step 4
View a summary of the
EtherChannel configuration on the device.
• Enter
show etherchannel summary. Step 5
View a
summary of the trunk status of any ports that are in trunking
mode.
• Enter show interfaces trunk. Step
6
View details about the spanning tree status on the
device.
• Depending on the IOS version, enter
show spanning-tree or show spantree. Step 7
View a list of directly connected Cisco devices.
•
Enter show cdp neighbors. Step 8
View
details about any connected devices such as IP address and
capabilities.
• Enter show cdp entry {entry
name}. All this information can be displayed using the
command show tech-support. However, the output from this
command will generate a lot more information than is actually
needed.
Content 1.2 Network Configuration
Documentation 1.2.5 Describing the process of
creating network documentation For the process of creating
network documentation it is recommended that the network
configuration table and topology diagram be created together.
It is beneficial to create one type of document first,
depending on the specific needs and amount of documentation
already available.
Content 1.2 Network
Configuration Documentation 1.2.6 Creating
network documentation Good network configuration
documentation allows rapid discovery of specific information
about network devices. Guidelines for creating effective
network documentation are: - Know which end systems are