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Exit Zen
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../../exercises/routing-protocols.rst:378
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Exploring BGP
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../../exercises/routing-protocols.rst:380
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To explore the configuration of BGP, let us consider a network that contains three ASes: ``AS1``, ``AS2`` and ``AS3``. To simplify the tests, we identify one host inside each of these ASes.
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../../exercises/routing-protocols.rst:434
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As in the previous examples, we create the routers and associate one IPv6 prefix to each AS:
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../../exercises/routing-protocols.rst:436
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``AS1`` is assigned ``2001:cafe:1::/48``
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../../exercises/routing-protocols.rst:437
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``AS2`` is assigned ``2001:cafe:2::/48``
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../../exercises/routing-protocols.rst:438
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``AS3`` is assigned ``2001:cafe:3::/48``
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../../exercises/routing-protocols.rst:454
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The `addDaemon` method adds a BGP daemon on each router and configures it to advertise the IPv6 prefix allocated to this AS. We then create all the links and manually assign one IPv6 subnet to each link and one IPv6 address to each interface. For the interdomain links, we use an IPv6 prefix that belongs to one of the attached ASes.
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../../exercises/routing-protocols.rst:491
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The last step is to specify to which AS each router belongs and to configure the eBGP sessions and their routing policies. IPMininet_ abstracts most of the complexity of the configuration of these policies by supporting two policies
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../../exercises/routing-protocols.rst:510
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The script ends by launching the full topology. The entire script is available from :download:`/exercises/ipmininet_scripts/ebgp-simple.py`.
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../../exercises/routing-protocols.rst:512
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We can now run this simple network.
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../../exercises/routing-protocols.rst:518
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If you launch the script and immediately type ``ping6all`` to check the connectivity, you might obtained the following result.
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../../exercises/routing-protocols.rst:529
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Remember that BGP is a distributed protocol and that it takes some time to launch the daemons and exchange the messages. After some time, the same command will confirm that everything works as expected.
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../../exercises/routing-protocols.rst:540
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We can also use :manpage:`traceroute6(8)` to check the path followed by the packets. Before doing that, think about the configuration of the BGP routing policies and try to predict the output of :manpage:`traceroute6(8)`. This is a good exercise to check your understanding of BGP.
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../../exercises/routing-protocols.rst:542
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We have configured the following addresses on the hosts.
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../../exercises/routing-protocols.rst:559
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We can now explore the routes in this small Internet. Host ``h1`` can reach directly host ``h3``.
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../../exercises/routing-protocols.rst:569
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Note that the path preferred by ``AS3`` to reach ``AS1`` is different.
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../../exercises/routing-protocols.rst:581
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The same applies for the paths between ``h1`` and ``h2``
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../../exercises/routing-protocols.rst:598
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Besides :manpage:`ping6(8)` and :manpage:`traceroute6(8)`, it is also useful to interact with the BGP daemon that runs on each of our routers. This is done by connecting on the Command Line Interface of the BGP router using telnet.
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../../exercises/routing-protocols.rst:619
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The password for the BGP daemon is `zebra`. The `noecho` command indicates that mininet_ does not need to echo the characters that you type. You then enter the Quagga VTY that enables you to type commands. The `help` commands gives you some information about the available commands as well as `?`.
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../../exercises/routing-protocols.rst:649
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In these exercises, we mainly consider the ``show`` that extracts information from the BGP daemon. We type `show bgp` and press the `tabulation` key to see the available commands in the `show bgp`.
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