Added adding static route before startup interfaces

[alawing]

Description of PR

Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

There are new arp and ndp behaviors when shutdown the interfaces:

How did you do it?

We changed and fixed the way of previous fixing to match the new arp and ndp behaviors when shutdown the interfaces:
#14251
We added adding static route before startup interfaces when running testing.

How did you verify/test it?

Tested the script

Any platform specific information?

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

Documentation

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/ecmp/test_fgnhg.py:275:13: E117 over-indented
tests/ecmp/test_fgnhg.py:281:1: E302 expected 2 blank lines, found 1
tests/ecmp/test_fgnhg.py:344:5: E265 block comment should start with '# '
tests/ecmp/test_fgnhg.py:413:5: E265 block comment should start with '# '

flake8...............................................(no files to check)Skipped
check conditional mark sort..........................(no files to check)Skipped

To run the pre-commit checks locally, you can follow below steps:

1. Ensure that default python is python3. In sonic-mgmt docker container, default python is python2. You can run
   the check by activating the python3 virtual environment in sonic-mgmt docker container or outside of sonic-mgmt
   docker container.
2. Ensure that the pre-commit package is installed:

sudo pip install pre-commit

3. Go to repository root folder
4. Install the pre-commit hooks:

pre-commit install

5. Use pre-commit to check staged file:

pre-commit

6. Alternatively, you can check committed files using:

pre-commit run --from-ref <commit_id> --to-ref <commit_id>

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/ecmp/test_fgnhg.py:275:13: E117 over-indented
tests/ecmp/test_fgnhg.py:289:5: E265 block comment should start with '# '

flake8...............................................(no files to check)Skipped
check conditional mark sort..........................(no files to check)Skipped

To run the pre-commit checks locally, you can follow below steps:

1. Ensure that default python is python3. In sonic-mgmt docker container, default python is python2. You can run
   the check by activating the python3 virtual environment in sonic-mgmt docker container or outside of sonic-mgmt
   docker container.
2. Ensure that the pre-commit package is installed:

sudo pip install pre-commit

3. Go to repository root folder
4. Install the pre-commit hooks:

pre-commit install

5. Use pre-commit to check staged file:

pre-commit

6. Alternatively, you can check committed files using:

pre-commit run --from-ref <commit_id> --to-ref <commit_id>

[bingwang-ms]

/azp run Azure.sonic-mgmt

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[bingwang-ms]

Where is the static neighbor removed?

[alawing]

From 202205 and newer version. When testing shut down an interface, the neighbor/Arp tables will lose the static neighbor

[bingwang-ms]

My concern is the statically added neighbor will be there permanently, which may impact other tests running after test_fgnhg. Suggest adding a cleanup to remove the statically programmed neigh

[alawing]

Neighbor entries will be flushed when reloading config after tests.

[prsunny]

i thought we fixed it by sonic-net/sonic-swss#2469

[alawing]

i thought we fixed it by sonic-net/sonic-swss#2469

That PR is not fixing the issue we have on this test.

[mssonicbld]

Cherry-pick PR to 202305: #14868

[mssonicbld]

Cherry-pick PR to 202405: #14869

[mssonicbld]

Cherry-pick PR to 202311: #14870