\section{Networking}

\begin{frame}
   {Things to Check: Networking}

   \begin{itemize}

      \item IP configuration
      \item Network Driver
      \item Connectivity
      \item Default gateway and routing configuration
      \item Hostname resolution
   \end{itemize}

\end{frame}

\cprotect\note{
   \small{
      Network problems can be caused either by software or
      hardware, and can be as simple as is the device driver
      loaded, or is the network cable connected.  If the
      network is up and running but performance is terrible,
      it really falls under the banner of performance tuning,
      not troubleshooting. The problems may be external to the
      machine, or require adjustment of the various networking
      parameters including buffer sizes etc.

      The following items need to be checked when there are
      issues with networking:

      \begin{itemize}
         \item

         \textbf{IP configuration:}

         Use \textbf{ifconfig} or \textbf{ip} to see if the
         interface is up, and if so if it is configured

         \item
         \textbf{Network Driver:}

         If the interface cannot be brought up, maybe the
         correct device driver for the network card(s) is not
         loaded. Check with \textbf{lsmod} if the network
         driver is loaded as a kernel module, or by examining
         relevant pseudo-files in \filelink{/proc} and
         \filelink{/sys}, such as \filelink{/proc/interrupts}
         or \filelink{/sys/class/net}.

         \item

         \textbf{Connectivity:}

         Use \textbf{ping} to see if the network is visible,
         checking for response time and packet loss.
         \textbf{traceroute} can follow packets through the
         network, while \textbf{mtr} can do this in a
         continuous fashion.  Use of these utilities can tell
         you if the problem is local or on the Internet.

         \item

         \textbf{Default gateway and routing configuration:}

         Run \textbf{route -n} and see if the routing table
         make sense.

         \item

         \textbf{Hostname resolution:}

         Run \textbf{dig} or \textbf{host} on a URL and see if
         \textbf{DNS} is working properly.

      \end{itemize}
   }

}

