def METHOD_NAME(mod):
    "Sets up the pytest environment"
    tgen = Topogen(build_topo, mod.__name__)
    tgen.start_topology()
    router_list = tgen.routers()
    for rname, router in router_list.items():
        router.load_config(
            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
        )
        router.load_config(
            TopoRouter.RD_OSPF, os.path.join(CWD, "{}/ospfd.conf".format(rname))
        )
        # What is this?  OSPF Unnumbered depends on the rp_filter
        # being set appropriately( HA! )
        # Effectively we are putting different /32's on the interface
        # the multicast packet delivery is somewhat controlled by
        # the rp_filter.  Setting it to '0' allows the OS to pass
        # up the mcast packet not destined for the local routers
        # network.
        topotest.sysctl_assure(tgen.net["r1"], "net.ipv4.conf.r1-eth1.rp_filter", 0)
        topotest.sysctl_assure(tgen.net["r1"], "net.ipv4.conf.all.rp_filter", 0)
        topotest.sysctl_assure(tgen.net["r2"], "net.ipv4.conf.r2-eth1.rp_filter", 0)
        topotest.sysctl_assure(tgen.net["r2"], "net.ipv4.conf.all.rp_filter", 0)
    # Initialize all routers.
    tgen.start_router()
    # tgen.mininet_cli()