.. _example_protocols_bgp_parameters_distance:

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Distance
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Scenario to verify BGP **distance** (administrative distance) configuration.

Administrative distance is how a router decides which route to install when the same
destination is reachable through multiple routing protocols. Each protocol has a default
distance value, and the route with the lowest distance wins. The default values are:
eBGP external routes use **20**, iBGP internal routes use **200**, locally originated
routes use **200**, and static routes use **1**. This is why static routes typically
win over BGP when both exist for the same destination.

There are two commands to modify BGP distances. The first is ``distance global``, which
modifies the distance for **external** routes learned from eBGP peers, **internal**
routes learned from iBGP peers, and **local** routes originated locally. Each type can
be configured independently and uses its default value if not explicitly set. The second
command is ``distance prefix``, which sets the distance for all routes received from neighbors
whose IP address matches a given prefix. This is useful when you want different distances for
different BGP neighbors without changing the global settings.

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Test BGP Distance Global
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Description
===========

The ``distance global`` command modifies the administrative distance for all BGP
routes based on their type. It requires configuring all three values together:
external, internal, and local. This test first verifies the default behavior where
eBGP routes have distance 20 and static routes have distance 1, causing static to
win. Then it applies ``distance global external 5`` to lower the eBGP distance below
the static route distance of 10, making BGP the preferred path.

Scenario
========

.. include:: distance/testbgpdistanceglobal

.. raw:: html

  <hr>

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Test BGP Distance Prefix
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Description
===========

The ``distance prefix`` command provides fine-grained control by setting distance
based on the neighbor's IP address rather than changing global values. The prefix
parameter must match the neighbor's IP, not the routes being advertised. In this
scenario, **DUT0** assigns distance 15 to all routes received from neighbor
``10.10.0.200/32``. A static blackhole route with distance 10 is also configured.
Since 10 is lower than 15, the static route wins, demonstrating that prefix-based
distance is being applied to the BGP routes from that specific neighbor.

Scenario
========

.. include:: distance/testbgpdistanceprefix

.. raw:: html

  <hr>