This indicates whether this port is a member of a mesh group or blocked; circuits in the same mesh group act as a virtual multiaccess network, and LSPs seen on one circuit in a mesh group are not flooded to another circuit in the same group. Setting it to set(3) tells the router to treat this circuit as part of a logical multi-access group so it deliberately withholds re-flooding an LSP it already received from one meshgroup member back out to other members, cutting redundant flooding on networks with many parallel links between the same routers. For example, on a full mesh of point-to-point circuits between four core routers, putting all four routers' relevant circuits into the same mesh group prevents each LSP from being needlessly re-flooded three separate times.