\section{Spanning Tree}

Spanning Tree exists for the \textbf{sole} reason to save "your" network and all the broadcast storms an network engineer having a bad day can by mistake create!

STP comes from the above desire where redundancy was wanted but no protocol existed before STP to help in this regard.

\begin{table}[h]
	\centering
	\caption{Spanning Tree standrds}
	\label{stpstandards}
	\resizebox{\columnwidth}{!}{%
		\begin{tabular}{|l|l|l|l|l|}
			\hline
			\textbf{} & \textbf{Standard} & \textbf{Ressource Usage} & \multicolumn{2}{l|}{\textbf{Convergence}} \\ \hline
			CST       & 802.1D            & Low                      & Slow              & All vlans             \\ \hline
			PVST+     & Cisco             & High                     & Slow              & Per vlan              \\ \hline
			RSTP      & 802.1w            & So-so (Med.)             & Fast              & All vlans             \\ \hline
			RPVST+    & Cisco             & On-the-double (V.High)   & Fast              & Per vlan              \\ \hline
			MST       & 802.1s            & Med. - High              & Fast              & Vlan list             \\ \hline
		\end{tabular}%
	}
\end{table}

\subsection{Port Roles}

When a switch is enabled for Spanning Tree. One of the following roles will have been assumed by any port on the switch in question.

\begin{itemize}
	\item \textbf{Root port:} Only 1 port on any switch (non-counting the root bridge!). Is always the port with the lowest metric (aka. best path) to the root bridge.
	\item \textbf{Designated port:} A designated port is the port on any segment closest to the root bridge and forwarding traffic.
	\item \textbf{\textit{Non}-designated port:} Put in blocking mode and not currently forwarding traffic.
	\item \textbf{Disabled port:} The port has been one-way-or-another shut down.
\end{itemize}

\subsection{Standards}

\subsubsection{STP}

\subsubsection{PVST}

\subsubsection{RPVST+}

\subsubsection{MST}

\subsection{Features}

\begin{itemize}
	\item PortFart
	\item UplinkFast
	\item BackboneFast
	\item BPDU Guard
	\item BPDU Filter
	\item Root Guard
	\item Loop Guard
	\item Unidirectional Link Detection (UDLD)
	\item FlexLinks
\end{itemize}
