def METHOD_NAME():
    "Assert that BGP is converging after setting a link down."
    tgen = get_topogen()
    if tgen.routers_have_failure():
        pytest.skip(tgen.errors)
    logger.info("waiting for BGP re convergence")
    # Check that BGP converged quickly.
    for router in tgen.routers().values():
        ref_file = "{}/{}/bgp_prefixes.json".format(CWD, router.name)
        expected = json.loads(open(ref_file).read())
        # Load the same file as previous test, but set networks to None
        # to test absence.
        if router.name == "r1":
            expected["routes"]["10.254.254.2/32"] = None
            expected["routes"]["10.254.254.3/32"] = None
            expected["routes"]["10.254.254.4/32"] = None
        else:
            expected["routes"]["10.254.254.1/32"] = None
        test_func = partial(
            topotest.router_json_cmp, router, "show ip bgp json", expected
        )
        _, res = topotest.run_and_expect(test_func, None, count=5, wait=1)
        assertmsg = "{}: bgp did not converge".format(router.name)
        assert res is None, assertmsg