fix default route for t0-isolated topo by sdszhang · Pull Request #22565 · sonic-net/sonic-mgmt

sdszhang · 2026-02-24T12:09:37Z

Description of PR

Summary:
In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it.

Fixes default route for t0-isolated topo.

route/test_default_route.py::test_default_route_with_bgp_flap FAILED     [ 75%]
......
        logging.info("peer intf ip from tb {}".format(upstream_neigh_ip))
>       pytest_assert(len(nexthops) == len(upstream_neigh_ip),
                      "Default route nexthops doesn't match the testbed topology")
E       Failed: Default route nexthops doesn't match the testbed topology

Type of change

Back port request

Approach

What is the motivation for this PR?

Fix default route announcement from PT0 in t0-isolated topo

How did you do it?

advertise default for PT0 neighbor.
update test_default_route.py test case to use PT0 only as upstream neighbor.

How did you verify/test it?

local testbed.

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

mssonicbld · 2026-02-24T12:09:44Z

/azp run

azure-pipelines · 2026-02-24T12:09:58Z

Azure Pipelines successfully started running 1 pipeline(s).

sdszhang · 2026-02-24T12:12:55Z

local test result on 202412:

route/test_default_route.py::test_default_route_set_src PASSED           [ 25%]
route/test_default_route.py::test_default_ipv6_route_next_hop_global_address PASSED [ 50%]
route/test_default_route.py::test_default_route_with_bgp_flap PASSED     [ 75%]
route/test_default_route.py::test_ipv6_default_route_table_enabled_for_mgmt_interface PASSED [100%]
......
=================== 4 passed, 2 warnings in 97.45s (0:01:37) ===================

r12f · 2026-02-24T13:00:04Z

Will this break other tests?

r12f · 2026-02-24T15:45:12Z

this is a fairly large change, and I would recommend run a full test run before commit this in.

sdszhang · 2026-02-25T22:21:01Z

this is a fairly large change, and I would recommend run a full test run before commit this in.

Hi @r12f , there is no new failure with this change: https://elastictest.org/scheduler/testplan/699da1eb32ebdf0ced87b34e

StormLiangMS

Please confirm the route generation callees (e.g. \generate_routes) accept \ or_default_route\ as a keyword argument — otherwise this will raise a \TypeError\ at runtime.

yxieca

AI agent on behalf of Ying: Note that this adds tor_default_route to the generate_routes call. I don’t see the corresponding parameter addition in the helper; please confirm the callee accepts this kwarg or update it, otherwise we’ll hit a TypeError at runtime. (Echoing StormLiangMS’ concern.)

yxieca

AI agent on behalf of Ying: Confirmed generate_routes already accepts tor_default_route in announce_routes.py; change looks good. Approving.

yxieca · 2026-02-27T23:28:08Z

@sdszhang there is a merge conflict, can you check?

yxieca

LGTM. AI agent on behalf of Ying.

yxieca

Looks good. The PT-only neighbor filter for t0-isolated makes the default-route check match topology preference, and tor_default_route gating aligns announce_routes behavior. AI agent on behalf of Ying.

yxieca

LGTM. Change is scoped and aligns the test expectation with PT0-preferred default route behavior in t0-isolated. (AI agent on behalf of Ying)

yxieca

Looks good to me. The PT-only upstream filter for t0-isolated aligns with the preferred default route behavior and the announce_routes tweak is consistent with existing tor_default_route handling.\n\nAI agent on behalf of Ying.

mssonicbld · 2026-03-01T22:16:38Z

/azp run

azure-pipelines · 2026-03-01T22:16:52Z

Azure Pipelines successfully started running 1 pipeline(s).

Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> # Conflicts: # tests/route/test_default_route.py

mssonicbld · 2026-03-01T22:17:38Z

/azp run

azure-pipelines · 2026-03-01T22:17:51Z

Azure Pipelines successfully started running 1 pipeline(s).

mssonicbld · 2026-03-06T10:47:31Z

/azp run

azure-pipelines · 2026-03-06T10:47:46Z

Azure Pipelines successfully started running 1 pipeline(s).

r12f

agreed with no pick to 202412. LGTM

dayouliu1 · 2026-03-11T21:14:31Z

local test result on 202412:

route/test_default_route.py::test_default_route_set_src PASSED           [ 25%]
route/test_default_route.py::test_default_ipv6_route_next_hop_global_address PASSED [ 50%]
route/test_default_route.py::test_default_route_with_bgp_flap PASSED     [ 75%]
route/test_default_route.py::test_ipv6_default_route_table_enabled_for_mgmt_interface PASSED [100%]
......
=================== 4 passed, 2 warnings in 97.45s (0:01:37) ===================

Just wondering if this test is passing for t0-isolated-d32u32s2 on 202412

sdszhang · 2026-03-11T22:27:12Z

local test result on 202412:

route/test_default_route.py::test_default_route_set_src PASSED           [ 25%]
route/test_default_route.py::test_default_ipv6_route_next_hop_global_address PASSED [ 50%]
route/test_default_route.py::test_default_route_with_bgp_flap PASSED     [ 75%]
route/test_default_route.py::test_ipv6_default_route_table_enabled_for_mgmt_interface PASSED [100%]
......
=================== 4 passed, 2 warnings in 97.45s (0:01:37) ===================

Just wondering if this test is passing for t0-isolated-d32u32s2 on 202412

The test will pass on 202412 with the cherry-pick in Azure/sonic-mgmt.msft#1037, even though no routes are coming from PT0 in 202412 after add-topo.
This PR is to fix the behavior where the default route is not being advertised by PT0 neighbors.

StormLiangMS

LGTM

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> Signed-off-by: mssonicbld <sonicbld@microsoft.com>

mssonicbld · 2026-03-13T00:47:11Z

Cherry-pick PR to 202511: #22933

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> Signed-off-by: mssonicbld <sonicbld@microsoft.com>

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> Signed-off-by: selldinesh <dinesh.sellappan@keysight.com>

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> Signed-off-by: Abhishek <abhishek@nexthop.ai>

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> Signed-off-by: Venkata Gouri Rajesh Etla <vrajeshe@cisco.com>

Description of PR Summary: In t0-isolated topo, the default route may come from PT0 or T1, and PT0 is preferred due to shorter AS path. Update the test case to suit it. Fixes default route for t0-isolated topo. route/test_default_route.py::test_default_route_with_bgp_flap FAILED [ 75%] ...... logging.info("peer intf ip from tb {}".format(upstream_neigh_ip)) > pytest_assert(len(nexthops) == len(upstream_neigh_ip), "Default route nexthops doesn't match the testbed topology") E Failed: Default route nexthops doesn't match the testbed topology Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com>

github-actions bot requested review from r12f, wangxin and xwjiang-ms February 24, 2026 12:09

StormLiangMS reviewed Feb 26, 2026

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yxieca reviewed Feb 27, 2026

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yxieca approved these changes Feb 27, 2026

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yxieca approved these changes Feb 28, 2026

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yxieca approved these changes Mar 1, 2026

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yxieca previously approved these changes Mar 1, 2026

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sdszhang dismissed yxieca’s stale review via 818e43d March 1, 2026 22:16

fix default route for t0-isolated topo

dd6a486

Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com> # Conflicts: # tests/route/test_default_route.py

sdszhang force-pushed the bgp_default_route branch from 818e43d to dd6a486 Compare March 1, 2026 22:17

sdszhang mentioned this pull request Mar 1, 2026

Fix test_default_route_with_bgp_flap for t0-isolated-d32u32s2 and related topos #21708

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sdszhang closed this Mar 6, 2026

sdszhang reopened this Mar 6, 2026

sdszhang added the Request for 202511 branch Request to backport a change to 202511 branch label Mar 8, 2026

r12f approved these changes Mar 11, 2026

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vmittal-msft added the Approved for 202511 branch label Mar 11, 2026

StormLiangMS approved these changes Mar 13, 2026

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StormLiangMS merged commit 1032966 into sonic-net:master Mar 13, 2026
27 of 28 checks passed

mssonicbld added the Created PR to 202511 branch label Mar 13, 2026

mssonicbld mentioned this pull request Mar 13, 2026

[action] [PR:22565] fix default route for t0-isolated topo #22933

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mssonicbld added Included in 202511 branch and removed Created PR to 202511 branch labels Mar 13, 2026

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Description of PR

Type of change

Back port request

Approach

What is the motivation for this PR?

How did you do it?

How did you verify/test it?

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

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