.. _example_protocols_bgp_parameters_bestpath:

########
Bestpath
########

Scenario to verify BGP **bestpath** parameter configuration.

The bestpath parameters control how BGP selects the best route when multiple
paths exist to the same destination. This test suite verifies the following
sub-commands: ``as-path ignore`` and ``compare-routerid``.

**DUT0** (AS 100) receives the same route from two eBGP neighbors (**DUT1**
and **DUT2**) with different attributes. The tests demonstrate how each
bestpath parameter changes the route selection behavior.

***********************************************************
Test eBGP - Bestpath as-path ignore changes route selection
***********************************************************

Description
===========

Test that ``bestpath as-path ignore`` causes BGP to ignore AS-path length
when selecting the best route. **DUT0** (AS 100) receives route
``192.168.10.0/24`` from **DUT1** (AS 200, MED 100, AS-path length 1) and
**DUT2** (AS 200, MED 50, AS-path length 2). Without the parameter, the
shorter AS-path wins. With the parameter, AS-path is ignored and MED
determines the selection.

Scenario
========

.. include:: bestpath/testebgp-bestpathas-pathignorechangesrouteselection

.. raw:: html

  <hr>

*********************************************************************
Test eBGP - Bestpath compare-routerid enables deterministic selection
*********************************************************************

Description
===========

Test that ``bestpath compare-routerid`` uses router-id as a deterministic
tie-breaker for identical eBGP paths. **DUT0** (AS 100) receives route
``192.168.10.0/24`` from **DUT1** (AS 200, router-id 10.255.255.100) and
**DUT2** (AS 200, router-id 10.255.255.50). Without the parameter, the
older path wins. With the parameter, the lower router-id wins.

Scenario
========

.. include:: bestpath/testebgp-bestpathcompare-routeridenablesdeterministicselection

.. raw:: html

  <hr>