diff --git a/chapter/section/spanningtree.tex b/chapter/section/spanningtree.tex index cc319a5..0ab1cd6 100644 --- a/chapter/section/spanningtree.tex +++ b/chapter/section/spanningtree.tex @@ -11,20 +11,20 @@ Spanning Tree exists for the \textbf{sole} reason to save "your" network and all 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}% - } + \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} @@ -32,25 +32,25 @@ STP comes from the above desire where redundancy was wanted but no protocol exis 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{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. \begin{itemize} \item The upstream/-link port closest to the root bridge on all switches apart from the root bridge. \end{itemize} - \item \textbf{Designated port:} A designated port is the port on any segment closest to the root bridge and forwarding traffic. + \item \textbf{Designated port:} A designated port is the port on any segment closest to the root bridge and forwarding traffic. \begin{itemize} \item The port on any switch in downstream direction closet to the root bridge. \end{itemize} - \item \textbf{\textit{Non}-designated port:} Put in blocking mode and not currently forwarding traffic. + \item \textbf{\textit{Non}-designated port:} Put in blocking mode and not currently forwarding traffic. \begin{itemize} \item All switch ports which did not get elected as the root or designated port. \end{itemize} - \item \textbf{Disabled port:} The port has been one-way-or-another shut down. + \item \textbf{Disabled port:} The port has been one-way-or-another shut down. \end{itemize} \subsubsection{specific port roles} \begin{itemize} - \item \textbf{Alternative port} is an active port in network with an alternative path to the root bridge. A port in alternative mode will remain active but \textit{discards} all traffic until the the current designated path fails. - \item \textbf{Backup port} is running in active mode and \textit{discards} all traffic it recieves until the current designated port on the segment the backup port is connected to, fails. + \item \textbf{Alternative port} is an active port in network with an alternative path to the root bridge. A port in alternative mode will remain active but \textit{discards} all traffic until the the current designated path fails. + \item \textbf{Backup port} is running in active mode and \textit{discards} all traffic it recieves until the current designated port on the segment the backup port is connected to, fails. \end{itemize} Election of ports goes in order of the following values (low is best): 1) root bridge id, 2) lowest path cost to root bridge, 3) sender bridge id, 4) sender port bridge id @@ -123,18 +123,18 @@ Using a \textbf{R}oot \textbf{B}rigde as the reference point for the STP instanc \subsubsection{Port Cost} \begin{table}[h] - \centering - \caption{Default port cost in spanning tree} - \label{stpportcost}{!}{% - \begin{tabular}{|l|l|} - \hline - \textbf{Link} & \textbf{Default Cost} \\ \hline - 10 Gbps & 1 \\ \hline - 1 Gbps & 4 \\ \hline - 100 Mbps & 19 \\ \hline - 10 Mbps & 100 \\ \hline - \end{tabular}% - } + \centering + \caption{Default port cost in spanning tree} + \label{stpportcost}{!}{% + \begin{tabular}{|l|l|} + \hline + \textbf{Link} & \textbf{Default Cost} \\ \hline + 10 Gbps & 1 \\ \hline + 1 Gbps & 4 \\ \hline + 100 Mbps & 19 \\ \hline + 10 Mbps & 100 \\ \hline + \end{tabular}% + } \end{table} \fig{spanningtree/portroles}{stpportroles}{Port Election} @@ -266,7 +266,7 @@ Cisco did on their part early on enhance the original spanning tree standard wit \subsection{Link} \begin{itemize} - \item Unidirectional Link Detection (UDLD) + \item Unidirectional Link Detection (UDLD) \begin{itemize} \item Cisco proprietary feature. \item By default only enables on fiber optic links. @@ -275,7 +275,17 @@ Cisco did on their part early on enhance the original spanning tree standard wit \item On ether-channel links with uni-directional link failures, udld will disable individual failed links. \item For the best protection. Aggresive mode is recommended. \item It is recommended to turn on udld in global conf mode. - \item FlexLinks + \item FlexLinks + \begin{itemize} + \item Cisco proprietary feature. + \item An alternate solution to running STP in the environment. + \begin{itemize} + \item STP is auto-disabled on interfaces running FlexLinks. + \item Configured with 2 physical links with and active/backup configuration. + \item Enables convergence time of less than 50 milliseconds. + \end{itemize} + \item FlexLinks is good alternative to running STP in an environment with customers who you do \texit{not} want to run STP with. Fx. Service Provider/Enterprise/Datacenter environment. + \end{itemize} \end{itemize} \begin{table}[h]