diff --git a/CHANGELOG.md b/CHANGELOG.md
index e69de29..9faed70 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -0,0 +1,17 @@
+# Change Log
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+### Added
+
+### Changed
+
+## [0.1.0-lw] - 2017-05-30
+### Added
+- Initial version
+- Section: Spanning Tree
+
+[Unreleased]: https://gitlab.com/netravnen/CiscoLabNotes/compare/v0.1.0-lw...HEAD
\ No newline at end of file
diff --git a/chapter/layer3protocols.tex b/chapter/layer3protocols.tex
index 3227f5d..71a2db9 100644
--- a/chapter/layer3protocols.tex
+++ b/chapter/layer3protocols.tex
@@ -1,6 +1,7 @@
+\chapter{Layer-2-to-Layer-3}
+
+\input{chapter/section/intervlanrouting}
+
 \chapter{Protocols Layer 3}
 
 \input{chapter/section/routednetwork}
-
-\newpage
-
diff --git a/chapter/section/intervlanrouting.tex b/chapter/section/intervlanrouting.tex
new file mode 100644
index 0000000..7eed6ba
--- /dev/null
+++ b/chapter/section/intervlanrouting.tex
@@ -0,0 +1 @@
+\section{Vlan-to-vlan routing}
\ No newline at end of file
diff --git a/chapter/section/spanningtree.tex b/chapter/section/spanningtree.tex
index 7dc40dc..7746964 100644
--- a/chapter/section/spanningtree.tex
+++ b/chapter/section/spanningtree.tex
@@ -377,9 +377,28 @@ It is the network admins job to propagate an even configuration to all switches
 
 \fig{spanningtree/mstregions2}{mstregions2}{MST Regions vlans mapped to different instances.}
 
-\begin{lstlisting}[language=TeX,numbers=none,frame=trBL,frameround=fttt,backgroundcolor=\color{white}]
+\pagebreak % avoids column break for the following text
+
+\begin{txt}
+|<-------- bridge id ----------->|
+
 +----------+-----------+---------+
 | Bridge   | Extended  | MAC     |
 | priority | system ID | Address |
 +----------+-----------+---------+
-\end{lstlisting}
\ No newline at end of file
+
+                /\
+                ||
+    MST inst. no. carried in
+      Ext. Syst. ID Area
+\end{txt}
+
+\subsection{Common Troubleshooting}
+
+\begin{itemize}
+    \item Duplex mismatch: Mismatch half/full duplex.
+    \item Unidirectional link failure
+    \item Frame corruption: Physical interfaces can be defective/with errors.
+    \item Resource errors: High compute usage in the Control Plane. {\scriptsize Remember the Spanning Tree Process in fx. Cisco Catalyst switches is handled in software.}
+    \item PortFast configuration error: Can lead to bridging loops when mis-wiring happens together with logical port configuration errors.
+\end{itemize}
diff --git a/commands.tex b/commands.tex
index 6e1e5ff..b97f2fb 100644
--- a/commands.tex
+++ b/commands.tex
@@ -47,4 +47,13 @@
 }
 
 \newcommand{\itemtitle}[2]{\textbf{#1:}\\%
-    {\footnotesize #2}}
\ No newline at end of file
+    {\footnotesize #2}}
+
+
+% Enviroment @var txt
+% changes code styling to: in frame, white bg.
+\lstnewenvironment{txt}{\lstset{style=plaintxt}}{}
+
+
+% Enviroment @var cisco
+\lstnewenvironment{cisco}{\lstset{style=cisco}}{}
\ No newline at end of file
diff --git a/structure.tex b/structure.tex
index aedc184..8239d6c 100644
--- a/structure.tex
+++ b/structure.tex
@@ -34,6 +34,9 @@
 \usepackage{fourier}
 \usepackage{array}
 \usepackage{makecell}
+\usepackage{inconsolata} 
+\usepackage{blindtext}
+\usepackage{expdlist} 
 
 
 \bibliographystyle{unsrtnat} %styles list https://www.sharelatex.com/learn/Natbib_bibliography_styles
@@ -108,6 +111,63 @@
 }
 
 
+\lstdefinestyle{plaintxt}{
+    language=TeX,
+    numbers=none,
+    frame=trBL,
+    frameround=fttt,
+    backgroundcolor=\color{white},
+    boxpos=c,
+}
+
+
+\lstdefinelanguage{cisco}{
+    keywords={
+        end,
+        hostname,
+        Interface int,
+        ip,
+        line,
+        login,
+        network,
+        no,
+        router,
+        sh,
+        show,
+        shut,
+        shutdown,
+        version,
+        vlan,
+        vrf,
+    },
+    keywordstyle=\color{blue}\bfseries,
+    ndkeywords={
+        addr,
+        address,
+        aux,
+        bgp,
+        con,
+        console,
+        dhcp,
+        eigrp,
+        g,
+        GigabitEthernet,
+        isis,
+        ospf,
+        ospfv3,
+        pool,
+        rip,
+        vty,
+    },
+    ndkeywordstyle=\color{darkgray}\bfseries,
+    identifierstyle=\color{black},
+    sensitive=false,
+    comment=[l]{!},
+    commentstyle=\color{purple}\ttfamily,
+    stringstyle=\color{red}\ttfamily,
+}
+
+
 \geometry{a4paper,margin=2cm}
 \setlength{\columnsep}{1.5cm} %space between columns
 \setlength{\headheight}{15pt}