Know what a network baseline is and the major components that go into making it. A
baseline is a set of documentation that establishes normal operating conditions on the network.
Some of the key components of a baseline are the network configuration tables, the
network topology diagrams, the end-system configuration tables, and the end-system topology
diagrams.
Know what network configuration tables are and the information they contain. Network
configuration tables are used to record key settings of network devices, as well as other related
information. Some common items included in a network configuration table are device name,
flash information, DRAM, IOS/CatOS, interface number, MAC address, speed, duplex,
VLANs, trunking, IP address, subnet, subnet mask, and routing protocol.
Know what network topology diagrams are and the information they contain. Network
topology diagrams are graphical representations of the network; they are usually built from
many of the same components as the network configuration tables. Some common components
of network topology diagrams are device name, connections between devices, interface name,
VLANs, trunking, IP address, subnet mask, and routing protocols. 1064
IT Certification CCIE,CCNP,CCIP,CCNA,CCSP,Cisco Network Optimization and Security Tips
Network Documentation salmon Summary
Documentation is essential in today’s increasingly complex networks. It provides vital information
that can greatly reduce network downtime. It also provides verification that the network
is operating correctly.
Baseline information on a network is information about the normal operating conditions of a
network. This baseline is used to determine whether a network configuration is set up in the manner
expected and whether it is operating normally. Some of the specific components of the network
baseline are the network configuration tables, the network topology diagrams, the endsystem
configuration tables, and the end-system topology diagrams.
Network configuration tables show the key configuration parameters that are in place on the
network devices. Some typical items included in a network configuration table are device name,
flash memory DRAM, IOS/CatOS, interface number, MAC address, speed, duplex, VLANs,
trunking, IP address, subnet, subnet mask, and routing protocol. Although these are some of the
standard items in a network configuration table, each table will vary based on a device’s type
and on the design of the particular network. In most cases this information is stored in a spreadsheet
or database format, but hard copies should be regularly printed so that information will
always be available in the event of a problem or failure.
Network topology diagrams are graphical representations of the network components, and
in most cases they contain a subset of the data maintained in the network configuration tables.
The topology diagrams are meant to make the network administrator better able to visualize the
path across the network. Some standard items that go into a network topology are device name,
connections between devices, interface name, VLANs, trunking, IP address, subnet mask, and
routing protocols. As is true for the network configuration tables, hard copies of network topology
diagrams should be regularly printed to ensure that information is always available when
the network goes down.
that can greatly reduce network downtime. It also provides verification that the network
is operating correctly.
Baseline information on a network is information about the normal operating conditions of a
network. This baseline is used to determine whether a network configuration is set up in the manner
expected and whether it is operating normally. Some of the specific components of the network
baseline are the network configuration tables, the network topology diagrams, the endsystem
configuration tables, and the end-system topology diagrams.
Network configuration tables show the key configuration parameters that are in place on the
network devices. Some typical items included in a network configuration table are device name,
flash memory DRAM, IOS/CatOS, interface number, MAC address, speed, duplex, VLANs,
trunking, IP address, subnet, subnet mask, and routing protocol. Although these are some of the
standard items in a network configuration table, each table will vary based on a device’s type
and on the design of the particular network. In most cases this information is stored in a spreadsheet
or database format, but hard copies should be regularly printed so that information will
always be available in the event of a problem or failure.
Network topology diagrams are graphical representations of the network components, and
in most cases they contain a subset of the data maintained in the network configuration tables.
The topology diagrams are meant to make the network administrator better able to visualize the
path across the network. Some standard items that go into a network topology are device name,
connections between devices, interface name, VLANs, trunking, IP address, subnet mask, and
routing protocols. As is true for the network configuration tables, hard copies of network topology
diagrams should be regularly printed to ensure that information is always available when
the network goes down.
Items from the switch configuration table
The following are examples of the output of each command:
salmon#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
marlin Ser 0/0 172 R 3640 Ser 0/0
069017443(switch_a) Eth 0/0 141 T B S WS-C5500 2/13
10.254.254.0/24
Network
VLAN 45
Server Segment
E0/0 Salmon
S0/0 S0/0
FA0/1
FA1/1
FA0/0
7/2
Trunk
E0/0 - 10.254.254.1/24
S0/0 10.10.10.1/30
FA0/1 - 10.20.20.1/24
S0/0 10.10.10.2/30
Management Interface VLAN 2
10.40.40.2
FA0/0.2 - 10.440.40.1/30
FA0/0.45 - 10.45.45.1/24
FA0/0.46 - 10.46.46.1/24
FA1/1 - 10.20.20.2/24
Marlin
Tuna
Core_Switch
EIGRP 200
OSPF 21
Device Name,
Model Location FlashDRAMCATOS
Mgmt
IP
VTP
Domain VTP Mode Port Speed Duplex VLAN(s)
STP State
(Fwd/Block)
Portfast
(Yes/No)
Trunk
(Yes/No
core_switch,
6509
Dover,
DE 16 64 6.4(3) 10.40.40.2 dover_coreTransparent 1/1 1000 Full 1,2,45,46 Fwd No Yes
1/2 1000 Full 1,2,45,46 Block No Yes
3/1 100 Full 45 Fwd Yes No
3/2 10 Half 45 Fwd Yes No
3/3 A-100 A-Full 45 Fwd Yes No
salmon#show cdp neighbors detail
-------------------------
Device ID: marlin
Entry address(es):
IP address: 10.10.10.2
Platform: cisco 3640, Capabilities: Router
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 160 sec
Version :
Cisco Internetwork Operating System Software
IOS (tm) 3600 Software (C3640-JS56I-M), Version 12.1(2), RELEASE
SOFTWARE (fc2)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Thu 08-Dec-00 04:50 by phanguye
-------------------------
Device ID: 069017443(switch_a)
Entry address(es):
IP address: 10.254.254.102
Platform: WS-C5500, Capabilities: Trans-Bridge Source-Route-Bridge
Switch
Interface: Ethernet0/0, Port ID (outgoing port): 2/13
Holdtime : 130 sec
Version :
WS-C5500 Software, Version McpSW: 4.5(5) NmpSW: 4.5(5)
Copyright (c) 1995-1999 by Cisco Systems
Because these commands are available in both routers and switches, you can
effectively move across the network one device at a time, documenting each
neighbor along the way.
One final recommendation: Accuracy is the key to any successful documentation strategy. As
things change in the network, your documents must be updated to reflect these changes. It is
usually best to get in the habit of changing your documents as a normal part of changing the network,
not as an afterthought. (This applies to scheduled changes as well as after troubleshooting!)
In this manner, you are less likely to get involved in other tasks and forget to update the
documentation.
salmon#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
marlin Ser 0/0 172 R 3640 Ser 0/0
069017443(switch_a) Eth 0/0 141 T B S WS-C5500 2/13
10.254.254.0/24
Network
VLAN 45
Server Segment
E0/0 Salmon
S0/0 S0/0
FA0/1
FA1/1
FA0/0
7/2
Trunk
E0/0 - 10.254.254.1/24
S0/0 10.10.10.1/30
FA0/1 - 10.20.20.1/24
S0/0 10.10.10.2/30
Management Interface VLAN 2
10.40.40.2
FA0/0.2 - 10.440.40.1/30
FA0/0.45 - 10.45.45.1/24
FA0/0.46 - 10.46.46.1/24
FA1/1 - 10.20.20.2/24
Marlin
Tuna
Core_Switch
EIGRP 200
OSPF 21
Device Name,
Model Location FlashDRAMCATOS
Mgmt
IP
VTP
Domain VTP Mode Port Speed Duplex VLAN(s)
STP State
(Fwd/Block)
Portfast
(Yes/No)
Trunk
(Yes/No
core_switch,
6509
Dover,
DE 16 64 6.4(3) 10.40.40.2 dover_coreTransparent 1/1 1000 Full 1,2,45,46 Fwd No Yes
1/2 1000 Full 1,2,45,46 Block No Yes
3/1 100 Full 45 Fwd Yes No
3/2 10 Half 45 Fwd Yes No
3/3 A-100 A-Full 45 Fwd Yes No
salmon#show cdp neighbors detail
-------------------------
Device ID: marlin
Entry address(es):
IP address: 10.10.10.2
Platform: cisco 3640, Capabilities: Router
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 160 sec
Version :
Cisco Internetwork Operating System Software
IOS (tm) 3600 Software (C3640-JS56I-M), Version 12.1(2), RELEASE
SOFTWARE (fc2)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Thu 08-Dec-00 04:50 by phanguye
-------------------------
Device ID: 069017443(switch_a)
Entry address(es):
IP address: 10.254.254.102
Platform: WS-C5500, Capabilities: Trans-Bridge Source-Route-Bridge
Switch
Interface: Ethernet0/0, Port ID (outgoing port): 2/13
Holdtime : 130 sec
Version :
WS-C5500 Software, Version McpSW: 4.5(5) NmpSW: 4.5(5)
Copyright (c) 1995-1999 by Cisco Systems
Because these commands are available in both routers and switches, you can
effectively move across the network one device at a time, documenting each
neighbor along the way.
One final recommendation: Accuracy is the key to any successful documentation strategy. As
things change in the network, your documents must be updated to reflect these changes. It is
usually best to get in the habit of changing your documents as a normal part of changing the network,
not as an afterthought. (This applies to scheduled changes as well as after troubleshooting!)
In this manner, you are less likely to get involved in other tasks and forget to update the
documentation.
Creating a Network Topology Diagram
Now that we have explained the purpose and suggested components for a network topology
diagram, let’s go through the steps to create one.
We will begin with an examination of the standard set of symbols used in such diagrams.
By now, most of you will have already seen and know these symbols; they are illustrated in
Figure 34.3. Employing a standard set of symbols for device types helps to ensure that any
new network administrators coming into the environment will be able to easily understand
the documentation.
FIGURE 3 4 . 3 Networking symbols
In most cases, a network topology diagram is created after the network configuration tables
are set up, because the topology diagram uses much of the information contained in the configuration
tables. Figure 34.4 illustrates a sample network topology diagram and its relationship
to some of the information used from the router configuration table.
Similarly, there is also a direct correlation between items on the topology diagram and the
switch network configuration table, as illustrated in Figure 34.5.
Because most of the information that is on the network topology diagram has already been
retrieved and placed in the network configuration tables, relatively few commands are needed
to generate the diagram itself. One command of great assistance is show cdp neighbors. The
Cisco Discovery Protocol (CDP) is a proprietary protocol that identifies directly attached Cisco
devices. This discovery is done at layer 2, so there is no need to have IP connectivity to see the
neighbors. The show cdp neighbor command shows the neighbors that have been learned via
CDP and gives their summary information. More detailed information can be found by using
the show cdp neighbors detail command.
Router Ethernet
connection
Switch Token Ring Token Ring
connection
Network that is not being
Network documented as part of this diagram
Serial/WAN
connection
diagram, let’s go through the steps to create one.
We will begin with an examination of the standard set of symbols used in such diagrams.
By now, most of you will have already seen and know these symbols; they are illustrated in
Figure 34.3. Employing a standard set of symbols for device types helps to ensure that any
new network administrators coming into the environment will be able to easily understand
the documentation.
FIGURE 3 4 . 3 Networking symbols
In most cases, a network topology diagram is created after the network configuration tables
are set up, because the topology diagram uses much of the information contained in the configuration
tables. Figure 34.4 illustrates a sample network topology diagram and its relationship
to some of the information used from the router configuration table.
Similarly, there is also a direct correlation between items on the topology diagram and the
switch network configuration table, as illustrated in Figure 34.5.
Because most of the information that is on the network topology diagram has already been
retrieved and placed in the network configuration tables, relatively few commands are needed
to generate the diagram itself. One command of great assistance is show cdp neighbors. The
Cisco Discovery Protocol (CDP) is a proprietary protocol that identifies directly attached Cisco
devices. This discovery is done at layer 2, so there is no need to have IP connectivity to see the
neighbors. The show cdp neighbor command shows the neighbors that have been learned via
CDP and gives their summary information. More detailed information can be found by using
the show cdp neighbors detail command.
Router Ethernet
connection
Switch Token Ring Token Ring
connection
Network that is not being
Network documented as part of this diagram
Serial/WAN
connection
Consistency and Simplicity Are the Keys
When creating network documentation, one goal that is frequently overlooked is the need to
make the documentation consistent and easy to read. Make an effort to apply the same structure
and methodology consistently to all the documentation. In this chapter we have discussed
the need for consistency when gathering the information and setting up a document, but it is
also important to maintain this uniformity from one document to the next.
One of the main purposes of your network documentation is its role in a troubleshooting
effort when the network is down. Because you can’t schedule when a problem will occur,
it is quite possible that you will be using your documentation to solve a problem in the middle
of the night, when you are not completely rested and are not operating at your peak
effectiveness. At such a time, you do not want to be saddled with documents that are
incompatible or so cluttered with information that they are difficult to read. Keep in mind
when and how the network documentation is going to be used, and take some simple steps
to make it easy to comprehend.
One of the first things you should do is ensure that the symbols used on all the diagrams mean
the same thing on each one. Do not use one symbol to signify a router on one diagram and a
different symbol to represent the same router on another.
Next, create a template for all your network configuration tables and topology diagrams. Earlier
in this chapter we discussed the template for a network configuration table, but templates for
network topology diagrams can be even more useful. For example, if you have multiple branch
locations, use an identical format and device-placement scheme on all the topology diagrams
so that similar information is always in the same spot on each diagram. This will save you time
in locating the facts you need.
Besides maintaining consistency, it is also important to avoid too much complexity. If the network
documentation contains extraneous information, that can make it difficult to find the
specifics that you need for your troubleshooting. The documentation should have enough
information to help you understand how things are connected and what the baseline of the
network is, without overwhelming you with data that may or may not be relevant.
make the documentation consistent and easy to read. Make an effort to apply the same structure
and methodology consistently to all the documentation. In this chapter we have discussed
the need for consistency when gathering the information and setting up a document, but it is
also important to maintain this uniformity from one document to the next.
One of the main purposes of your network documentation is its role in a troubleshooting
effort when the network is down. Because you can’t schedule when a problem will occur,
it is quite possible that you will be using your documentation to solve a problem in the middle
of the night, when you are not completely rested and are not operating at your peak
effectiveness. At such a time, you do not want to be saddled with documents that are
incompatible or so cluttered with information that they are difficult to read. Keep in mind
when and how the network documentation is going to be used, and take some simple steps
to make it easy to comprehend.
One of the first things you should do is ensure that the symbols used on all the diagrams mean
the same thing on each one. Do not use one symbol to signify a router on one diagram and a
different symbol to represent the same router on another.
Next, create a template for all your network configuration tables and topology diagrams. Earlier
in this chapter we discussed the template for a network configuration table, but templates for
network topology diagrams can be even more useful. For example, if you have multiple branch
locations, use an identical format and device-placement scheme on all the topology diagrams
so that similar information is always in the same spot on each diagram. This will save you time
in locating the facts you need.
Besides maintaining consistency, it is also important to avoid too much complexity. If the network
documentation contains extraneous information, that can make it difficult to find the
specifics that you need for your troubleshooting. The documentation should have enough
information to help you understand how things are connected and what the baseline of the
network is, without overwhelming you with data that may or may not be relevant.
Components of a Network Topology Diagram
Like the network configuration table, the network topology diagram can contain a number of
items; its scope will depend on the complexity of the network involved. In its simplest form, a
network topology diagram will only include the devices and the connections between them.
However, in most cases, the diagram will contain much more information. Some common items
are as follows:
Device Name
Connections Between Devices (which can also include circuit numbers on WAN links)
Device Type
Interface Name
Speed
Media Type
MAC Address
VLANs
Trunk
Encapsulation
IP Address
Subnet
Subnet Mask
Routing Protocols
Unlike the network configuration tables, it is quite common for the network topology diagram
to depict a combination of layer 2 and layer 3 devices. This allows for a more complete
view of the interactions in the network and a better overall view of network connectivity. Just
as you do with network configuration tables, however, you need to be careful to incorporate
enough information into the topology diagram without adding too much. These are working
documents; if they become too overloaded with information, their maintenance will be more
difficult. On the other side, you don’t want to be hunting down information in the middle of an
emergency. There is a delicate balance between too much and not enough information.
Another point of note: Unless your network is small, you are not going to be able to fit it into
a single network topology diagram. Typically, you will need to make multiple topology diagrams
that cover separate aspects of the network. Depending on the drawing program you are
using to create the diagrams, you can also link each of these separate topology diagrams
together. In this manner, you can double-click a particular area to see more- or less-detailed
information or move to another segment of the network.
items; its scope will depend on the complexity of the network involved. In its simplest form, a
network topology diagram will only include the devices and the connections between them.
However, in most cases, the diagram will contain much more information. Some common items
are as follows:
Device Name
Connections Between Devices (which can also include circuit numbers on WAN links)
Device Type
Interface Name
Speed
Media Type
MAC Address
VLANs
Trunk
Encapsulation
IP Address
Subnet
Subnet Mask
Routing Protocols
Unlike the network configuration tables, it is quite common for the network topology diagram
to depict a combination of layer 2 and layer 3 devices. This allows for a more complete
view of the interactions in the network and a better overall view of network connectivity. Just
as you do with network configuration tables, however, you need to be careful to incorporate
enough information into the topology diagram without adding too much. These are working
documents; if they become too overloaded with information, their maintenance will be more
difficult. On the other side, you don’t want to be hunting down information in the middle of an
emergency. There is a delicate balance between too much and not enough information.
Another point of note: Unless your network is small, you are not going to be able to fit it into
a single network topology diagram. Typically, you will need to make multiple topology diagrams
that cover separate aspects of the network. Depending on the drawing program you are
using to create the diagrams, you can also link each of these separate topology diagrams
together. In this manner, you can double-click a particular area to see more- or less-detailed
information or move to another segment of the network.
Network Topology Diagrams
Network configuration tables are great building blocks for your network documentation, but they
are not sufficient for getting a clear picture of how devices connect and interact within the network.
This is where the network topology diagram comes in. Simply put, a network topology diagram
is nothing more than a graphical representation of the network, allowing you to easily see
how components in the network are connected and how they interact. Arguably, it is the most
heavily utilized piece of documentation used in network troubleshooting and maintenance.
are not sufficient for getting a clear picture of how devices connect and interact within the network.
This is where the network topology diagram comes in. Simply put, a network topology diagram
is nothing more than a graphical representation of the network, allowing you to easily see
how components in the network are connected and how they interact. Arguably, it is the most
heavily utilized piece of documentation used in network troubleshooting and maintenance.
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