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\ihead{CCNA v7.0 Enterprise Networking, Security, and Automation}
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\ohead{kohnlehome.de/netz/CCNA-3-12.pdf}
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\ifoot{Franz Kohnle}
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\begin{document}

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    12 Network Troubleshooting
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\section*{12.1 Network Documentation}
\begin{itemize}
    \item Network Topology Diagrams
    \begin{itemize}
        \item Physical Topology: Device Name, Device location, Interface, ports used,  cable type
        \item Logical IPv4 Topology: Device id, IP/SM, Interface Id, Routing Protocols, Static routes, L2: VLANs, trunks, Etherchannel)
        \item Logical IPv6 Topology: evtl. eigenes Diagramm
    \end{itemize} 
    \item Network Device Documentation
    \begin{itemize}
        \item Router
        \item Switch
        \item End-system
    \end{itemize} 
    \item Network Baseline (normal network utilization)
    \begin{enumerate}
        \item Determine What Types of Data to Collect (z.B. interface utilization, CPU utilization)
        \item Identify Devices and Ports of Interest (uplink-ports, server, key-user)
        \item Determine the Baseline Duration  (2 bis 4 Wochen)
    \end{enumerate} 
\end{itemize}

\section*{12.2 Troubleshooting Process}
\begin{itemize}
    \item Seven-Step Troubleshooting Process
    \begin{enumerate}
        \item Define the Problem
        \item Gather Information
        \item Analyze information
        \item Eliminate Possible Causes
        \item Propose Hypothesis
        \item Test Hypothesis
        \item Solve the problem
    \end{enumerate}
    \item Question End Users
    \item Gather Information
    \begin{itemize}
        \item ping, traceroute, telnet, ssh
        \item show ip(v6) interface brief
        \item show ip(v6) route
        \item show protocols
        \item debug
    \end{itemize}
    \item Structured Troubleshooting Methods
    \begin{itemize}
        \item Bottom-Up: OSI-Layer 1-7
        \item Top-Down: OSI-Layer 7-1
        \item Divide-and-Conquer: OSI-Layer 3
        \item Follow-the-Path: traffic path from source to destination
        \item Substitution: swap-the-component
        \item Comparison: spot-the-differences (Vergleich mit funktionierenden Geräten, Konfigurationen)
        \item Educated Guess: shoot-from-the-hip
    \end{itemize}
\end{itemize}

\section*{12.3 Troubleshooting Tools}
\begin{itemize}
    \item Software Troubleshooting Tools: Network Management System Tools, Knowledge Bases, Baselining Tools 
    \item Protocol Analyzers: Wireshark
    \item Hardware Troubleshooting Tools
    \begin{itemize}
        \item Digital Multimeters
        \item Cable Testers
        \item Cable Analyzers (NEXT: near-end crosstalk, RL: return loss)
        \item Portable Network Analyzers
        \item Cisco Prime Network Analysis Module (NAM)
    \end{itemize}
    \item Syslog server
\end{itemize}

\section*{12.4 Symptoms and Causes of Network Problems}
\subsection*{Physical Layer Troubleshooting}
\begin{itemize}
    \item Symptoms
    \begin{itemize}
        \item Performance lower than baseline 
        \item Loss of connectivity
        \item Network bottlenecks or congestion
        \item High CPU utilization rates
        \item Console error messages          
    \end{itemize}
    \item Problem Cause
    \begin{itemize}
        \item Power-related  
        \item Hardware faults
        \item Cabling faults
        \item Attenuation (Dämpfung)
        \item Noise (EMI: electromagnetic interference)
        \item Interface configuration errors
        \item Exceeding design limits
        \item CPU overload
    \end{itemize}
\end{itemize}

\subsection*{Data Link Layer Troubleshooting}
\begin{itemize}
    \item Symptoms
    \begin{itemize}
        \item No functionality or connectivity at the network layer or above
        \item Network is operating below baseline performance levels
        \item Excessive broadcasts
        \item Console messages
    \end{itemize}
    \item Problem Cause
    \begin{itemize}
        \item Encapsulation errors
        \item Address mapping errors
        \item Framing errors
        \item STP failures or loops
    \end{itemize}
\end{itemize}

\subsection*{Network Layer Troubleshooting}
\begin{itemize}
    \item Symptoms
    \begin{itemize}
        \item Network failure
        \item Suboptimal performance
    \end{itemize}
    \item Problem Cause
    \begin{itemize}
        \item General network issues
        \item Connectivity issues
        \item Routing table
        \item Neighbor issues
        \item Topology database  
    \end{itemize}
\end{itemize}

\subsection*{Transport Layer Troubleshooting - ACLs}
\begin{itemize}
    \item Symptoms
    \begin{itemize}
        \item Connectivity issues
        \item Access Issues
    \end{itemize}
    \item Problem Cause
    \begin{itemize}
        \item ACL configurations
        \item NAT configurations  
    \end{itemize}
    \item Common ACL Misconfigurations
    \begin{itemize}
        \item Selection of traffic flow
        \item Order of access control entries
        \item Implicit deny any
        \item Addresses and IPv4 wildcard masks
        \item Selection of transport layer protocol
        \item Source and destination ports
        \item Use of the established keyword
        \item Uncommon protocols 
        \item Hilfreich: log keyword
    \end{itemize}
\end{itemize}

\subsection*{Transport Layer Troubleshooting - NAT for IPv4}
\begin{itemize}
    \item Common interoperability areas
    \begin{itemize}
        \item BOOTP and DHCP
        \item DNS and WINS
        \item SNMP
        \item tunneling and encryption protocols        
    \end{itemize}
\end{itemize}

\subsection*{Application Layer Troubleshooting}
\begin{itemize}
    \item SSH/Telnet, HTTP, FTP, TFTP, SMTP, POP
    \item SNMP
    \item DNS
    \item Network File System (NFS) 
\end{itemize}


\section*{12.5 Troubleshooting IP Connectivity}
\begin{itemize}
    \item ping, traceroute (für ipv4, ipv6)
    \item show interfaces G0/0/0 
    \begin{itemize}
        \item input/output queue drops / errors
        \item Full-duplex/Half-duplex 
    \end{itemize}
    \item MAC-Adressen, VLANs
    \begin{itemize}
        \item Windows: arp -a, netsh interface ipv6 show neighbor
        \item show ipv6 neighbors, show mac address-table
    \end{itemize}
    \item Default Gateway, Routing
    \begin{itemize}
        \item show ip route, show ipv6 route         
        \item show ipv6 interface GigabitEthernet 0/0/0
        \item Windows: ipconfig, route print
    \end{itemize}
    \item Transport-Layer: telnet mit anderen Ports
    \item ACLs: show ip access-lists, show ip interface    
\end{itemize}

\paragraph*{PT 12.5.13} Troubleshoot Enterprise Networks
\paragraph*{PT 12.6.1} Troubleshooting Challenge - Document the Network
\paragraph*{PT 12.6.2} Troubleshooting Challenge - Use Documentation to Solve Issues

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