Merge pull request FRRouting#20424 from opensourcerouting/fix/doc_allow_reserved_ranges

doc: Exclude 240.0.0.0/4 from allow-reserved-ranges

Author: donaldsharp

doc/user/basic.rst

@@ -313,15 +313,19 @@ Basic Config Commands
 
 .. clicmd:: allow-reserved-ranges
 
-   Allow using reserved ranges (e.g. 127.0.0.0/8, 0.0.0.0/8, 240.0.0.0/4).
+   Allow using reserved ranges (e.g. 127.0.0.0/8, 0.0.0.0/8).
 
    For example, this is necessary in case of multiple FRR instances
    (or FRR + any other daemon) peering via loopback interfaces
    running on the same router.
 
-   Another example is when you need to annouce a reserved range via
+   Another example is when you need to announce a reserved range via
    RIP protocol.
 
+   ``240.0.0.0/4`` is a reserved range too, but it's allowed by default,
+   because it's already widely used in private networks
+   (especially in data centers).
+
    Default: off.
 
 Line VTY Commands

tests/topotests/ripng_flush_time/__init__.py

@@ -0,0 +1,9 @@
+!
+int r1-eth0
+ ipv6 address 2001:db8::1/64
+!
+router ripng
+ network 2001:db8::/64
+ timers basic 5 15 30
+exit
+!

tests/topotests/ripng_flush_time/r1/frr.conf

@@ -0,0 +1,14 @@
+!
+int lo
+ ipv6 address 2001:db8:2::1/64
+!
+int r2-eth0
+ ipv6 address 2001:db8::2/64
+!
+router ripng
+ redistribute connected
+ network 2001:db8::/64
+ network 2001:db8:2::1/64
+ timers basic 5 15 30
+exit
+

tests/topotests/ripng_flush_time/r2/frr.conf

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+# Copyright (c) 2026 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+from lib import topotest
+from lib.topogen import Topogen, get_topogen
+
+pytestmark = [pytest.mark.ripngd]
+
+
+def setup_module(mod):
+    topodef = {"s1": ("r1", "r2")}
+    tgen = Topogen(topodef, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for _, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_frr_config(os.path.join(CWD, "{}/frr.conf".format(rname)))
+
+    tgen.start_router()
+
+
+def teardown_module():
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_ripng_flush_time():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+
+    def _show_routes(nh_num):
+        output = json.loads(r1.vtysh_cmd("show ipv6 route ripng json"))
+        expected = {
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_show_routes, 2)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Got routes, but metric is not set as expected"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))