Physical Topology:
* device type, model and manufacturer
* operating system version
* cable type and identifier
* cable specification - connector type
* cabling endpoints

Logical Topology:
device identifiers
* IP address and prefix lengths
* interface identifiers - connection type
* DLCI for virtual circuits
- site-to-site VPNs
* routing protocols = static routes
* data-link protocols
* WAN technologies used

Establishing a Network Baseline
Step 1: determine WHAT TYPES of data to collect
Step 2: identify devices and ports of interest
Step 3: determine the baseline duration

Commands that are useful to the network documentation process include:

* ping
* telnet
* show ip interface brief
* show ipv6 interface brief
* show ip route
* show ipv6 route
* show cdp neighbor detail

Gathering Symptoms
commands:
ping
traceroute
telnet
sho ip interface brief
show ipv6 interface brief
sho ip route
show ipv6 route
show running=config
debug (no debug = undebug)
show protocols

1. ask questions that are pertinent to the problem
2. use each question to either eliminate or discover possible problems
3. speak at technical level that user can understand
4. ask user when problem was first noticed
5. did anything unusual happen since last time it worked?
6. ask user to recreate the problem, if possible
7. determine the sequence of events that took place before the problem happened

Troubleshooting Methods
* bottom-up
* top-down
* divide-and-conquer


Other methods:
* educated guess
* compare working and nonworking situation
* swap problematic device with known working one

common software troubleshooting tools include:
* NMS tools
* knowledge bases
* baselining tools
* host-based protocol analyzers
* Cisco IOS EPC (embedded packet capture)

link to EPC article
https://supportforums.cisco.com/document/139686/configuration-example-embed...