With respect to digi, it's 802.15.4 firmware devices support point-to-point or point-to-multipoint. They do not support meshing or multihop.
It is possible however to load Digi's newer DigiMesh firmware on previous 802.15.4 firmware devices. This gives the Digi device the multi-hop meshing capabilities.
Digi's ZB firmware, which is based on Zigbee, is also multi-hop capable (Meshing).