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Exercises
We can use IPMininet_ to prepare some networks with problems that need to be analyzed and corrected.
Our first example is a small Internet with 5 ASes. A subset of the script that configures this network is shown below. There is one host attached to each AS and this host has the same number as its AS. The entire script is available from :download:`/exercises/ipmininet_scripts/ebgp-bug.py`.
When this network is launched, `ping6all` reports connectivity problems. Hosts `h1` and `h4` cannot exchange packets. Can you fix the problem by changing the routing policy used on only one interdomain link ? Justify your answer
Another interesting utilization IPMininet_ is to explore the impact of a link failure. We start from a small variant of the above topology.
When this network starts, all hosts can reach all other hosts.
Draw the network and try to predict how it will react to a shutdown of any of the customer-provider links ?
What are the BGP messages that will be exchanged when the link between ``AS1`` and ``AS2`` fails ? How does this affect the reachability of the different hosts ?
What are the BGP messages that will be exchanged when the link between ``AS1`` and ``AS3`` fails ? How does this affect the reachability of the different hosts ?
What are the BGP messages that will be exchanged when the link between ``AS1`` and ``AS5`` fails ? How does this affect the reachability of the different hosts ?
What are the BGP messages that will be exchanged when the link between ``AS3`` and ``AS4`` fails ? How does this affect the reachability of the different hosts ?
Let us now consider another example. The network contains nine ASes with one host per AS. Assuming that ``AS9`` announces prefix `p9` and that ``AS2`` announces prefix `p2`.
What is the Loc-RIB of ``AS6`` for prefix `p9` ? Indicate which is the best route towards this prefix.
What is the Loc-RIB of ``AS9`` for prefix `p2` ? Indicate which is the best route towards this prefix.
The network below contains nine ASes with one host per AS. Assuming that ``AS1`` announces prefix `p1` and that ``AS2`` announces prefix `p2`.
What is the Loc-RIB of ``AS6`` for prefix `p1` ? Indicate which is the best route towards this prefix.
What is the Loc-RIB of ``AS8`` for prefix `p2` ? Indicate which is the best route towards this prefix.
Let us now consider another example, also implemented using an IPMininet_ script. The network contains eight ASes with one host per AS. This small Internet is shown below and the script is available from :download:`/exercises/ipmininet_scripts/ebgp-bug-3.py`.
The network does not provide a full connectivity. The hosts attached to ``AS5`` cannot ping the hosts attached to ``AS8``.
What is the path that packets follow from a host attached to ``AS1`` to a host attached to ``AS8`` ?
What is the path that packets follow from a host attached to ``AS8`` to a host attached to ``AS1`` ?
What is the path that packets follow from a host attached to ``AS8`` to a host attached to ``AS2`` ?
What is the path that packets follow from a host attached to ``AS2`` to a host attached to ``AS7`` ?
We now disable the interdomain link between ``AS3`` and ``AS4``. What are the hosts that ``AS1``, ``AS5`` and ``AS6`` are still able to ping ?

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../../exercises/routing-protocols.rst:1265
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3 years ago
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locale/fr/LC_MESSAGES/exercises/routing-protocols.po, string 85