def METHOD_NAME():
    """
    Assert that BFD notices the link down after simulating network
    failure.
    """
    tgen = get_topogen()
    if tgen.routers_have_failure():
        pytest.skip(tgen.errors)
    # Disable r1-eth0 link.
    tgen.gears["r1"].link_enable("r1-eth0", enabled=False)
    # Wait the minimum time we can before checking that BGP/BFD
    # converged.
    logger.info("waiting for BFD converge")
    # Check that BGP converged quickly.
    for router in tgen.routers().values():
        json_file = "{}/{}/peers.json".format(CWD, router.name)
        expected = json.loads(open(json_file).read())
        # Load the same file as previous test, but expect R1 to be down.
        if router.name == "r1":
            for peer in expected:
                if peer["peer"] == "192.168.0.2":
                    peer["status"] = "down"
        else:
            for peer in expected:
                if peer["peer"] == "192.168.0.1":
                    peer["status"] = "down"
        test_func = partial(
            topotest.router_json_cmp, router, "show bfd peers json", expected
        )
        _, res = topotest.run_and_expect(test_func, None, count=20, wait=0.5)
        assertmsg = '"{}" JSON output mismatches'.format(router.name)
        assert res is None, assertmsg