The existence of multiple planetary systems involved in mean motion conmensurabilities has increased significantly since the Kepler mission .
Although most correspond to 2-planet resonances , multiple resonances have also been found .
The Laplace resonance is a particular case of a three-body resonance where the period ratio between consecutive pairs is n _ { 1 } / n _ { 2 } \sim n _ { 2 } / n _ { 3 } \sim 2 / 1 .
It is not clear how this triple resonance can act in order to stabilize ( or not ) the systems .

The most reliable extrasolar system located in a Laplace resonance is GJ 876 because it has two independent confirmations .
However best-fit parameters were obtained without previous knowledge of resonance structure and no exploration of all the possible stable solutions for the system where done .

In the present work we explored the different configurations allowed by the Laplace resonance in the GJ 876 system by varying the planetary parameters of the third outer planet .
We find that in this case the Laplace resonance is a stabilization mechanism in itself , defined by a tiny island of regular motion surrounded by ( unstable ) highly chaotic orbits .
Low eccentric orbits and mutual inclinations from -20 to 20 degrees are compatible with the observations .
A definite range of mass ratio must be assumed to maintain orbital stability .
Finally we give constrains for argument of pericenters and mean anomalies in order to assure stability for this kind of systems .