  Inelastic X-ray Scattering measurements of the dynamics structure factor have
bene performed on vitreous Beryllium Fluoride ({\it v-}BeF$_2$) at $T$=297 K in
the momentum transfer, $Q$, range $Q$=1.5$\div$10 nm$^{-1}$. We find evidence
of well defined high frequency acoustic modes. The energy position and
linewidth of the excitations disperse with $Q$ as $\propto Q$ and $\propto
Q^2$, respectively up to about one half of the first maximum of the static
structure factor. Their magnitude compare favorably with low-frequency sound
velocity and absorption data. The results indicate worth mentioning
similarities of the high frequency collective dynamics of different network
forming glasses such as {\it v-}B$_2$O$_3$ and {\it v-}SiO$_2$.
