\documentclass{article}
\usepackage{acronym}

\begin{document}

\section{Test section}
This is a test file for the acronyms.

Each time a \ac{bgp} advertisement traverses an \ac{AS}, the \ac{aspath}
attribute is modified. Additionally, \acp{AS} may introduce additional
changes in the \ac{aspath} for traffic engineering purposes.

Used following acronym macros

\begin{verbatim}
\usepackage{acronym}

\acrodef{AS}{Autonomous System}

\begin{acronym}
\acrodef{aspath}[AS\_PATH]{AS Path}
\acro{bgp}[BGP-4]{Border Gateway Protocol}
\acro{isis}[IS-IS]{IS-IS Protocol}
\acro{RIP}{RIPv2 Routing Protocol}
\end{acronym}
\end{verbatim}

Only \textbf{\ac{bgp}} should appear as an acronym in the acronym section.

\acrodef{AS}{Autonomous System}

\begin{acronym}
\acrodef{aspath}[AS\_PATH]{AS Path}
\acro{bgp}[BGP-4]{Border Gateway Protocol}
\acro{isis}[IS-IS]{IS-IS Protocol}
\acro{RIP}{RIPv2 Routing Protocol}
\end{acronym}

\end{document}
