Missing a vertical line in multicolumn table

Question

I have a table as shown below which is missing a horizontal line across a \multicolumn as shown below

The code I used is

\begin{figure}[!h]
\flushleft
  \begin{minipage}[c]{0.6\textwidth}
    \centering
  \includegraphics[width=1\linewidth,valign=c]{images/chap4/comparingThoughputQos0}
  \end{minipage}
\centering
  \begin{minipage}[c]{0.38\textwidth}
  \centering
    \renewcommand{\arraystretch}{1.0}
   \begin{tabular}{| c | c | c |}
    \hline
    \multirow{2}{*}{$\lambda_{{RE}}$}   & $NS_{{1}}$ & $NS_{{2}}$                \\ 
    \cline{2-3}
                                        & \multicolumn{2}{c}{$\mu_{RE-SCEPA}$}   \\
    \hline
    50   & 00   & 00   \\
    200  & 00   & 00   \\
    500  & 00   & 00   \\
    1000 & 00   & 00   \\
    2000 & 00   & 00   \\
    3000 & 00   & 00   \\
    \hline
    \end{tabular}         
    \end{minipage}
    \caption{Impact of number of sensors on $\mu_{RE}$ for different $\lambda_{{RE}}$}\label{fig:comparingThoughput}
 \end{figure}

What am I doing wrong?

Answer 1

Use

\multicolumn{2}{c|}{$\mu_{RE-SCEPA}$} 

               ^^^^

\multicolumn overwrites a previous definition