If $\vec{v}=\left(\begin{array}{l}2 \\ 2 \\ 2\end{array}\right)$ is an eigenvector of the matrix $\left(\begin{array}{lll}1 & 2 & 3 \\ 1 & 2 & 3 \\ 1 & 2 & 3\end{array}\right)$ corresponding to the non-zero eigenvalue, $\lambda$, then the value of $\lambda$ is $\_\_\_\_\_\_\_\_$.