  Using data from the NASA spacecraft Kepler, we study solar-like oscillations
in red-giant stars in the open cluster NGC6811. We determine oscillation
frequencies, frequency separations, period spacings of mixed modes and mode
visibilities for eight cluster giants. The oscillation parameters show that
these stars are helium-core-burning red giants. The eight stars form two groups
with very different oscillation power spectra; the four stars with lowest
Delta_nu-values display rich sets of mixed l=1 modes, while this is not the
case for the four stars with higher Delta_nu. For the four stars with lowest
Delta_nu, we determine the asymptotic period spacing of the mixed modes,
DeltaP, which together with the masses we derive for all eight stars suggest
that they belong to the so-called secondary clump. Based on the global
oscillation parameters, we present initial theoretical stellar modeling which
indicate that we can constrain convective-core overshoot on the main sequence
and in the helium-burning phase for these ~2M_sun stars. Finally, our results
indicate less mode suppression than predicted by recent theories for magnetic
suppression of certain oscillation modes in red giants.
