  We theoretically investigate the barrier tunneling in the three-dimensional
model of the hyperhoneycomb lattice, which is a nodal-line semimetal with a
Dirac loop at zero energy. In the presence of a rectangular potential, the
scattering amplitudes for different injecting states around the nodal loop are
calculated, by using analytical treatments of the effective model, as well as
numerical simulations of the tight binding model. In the low energy regime,
states with remarkable transmissions are only concentrated in a small range
around the loop plane. When the momentum of the injecting electron is coplanar
with the nodal loop, nearly perfect transmissions can occur for a large range
of injecting azimuthal angles if the potential is not high. For higher
potential energies, the transmission shows a resonant oscillation with the
potential, but still with peaks being perfect transmissions that do not decay
with the potential width. These robust transports of the loop-nodal semimetal
can be approximately explained by a momentum dependent Dirac Hamiltonian.
