msgid "" msgstr "" "Project-Id-Version: French (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-18 16:43+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: French \n" "Language: fr\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n > 1;\n" "X-Generator: Weblate 5.14.3\n" #: ../../exercises/routing-protocols.rst:9 #, rst-text msgid "" "Routing protocols play a key role in the Internet since they ensure that all " "the routers have valid routing tables. In this section, we use IPMininet_ to " "explore how intradomain and interdomain routing protocols work in practice. " "IPMininet_ adds an abstraction layer above the actual configuration of the " "FRRouting daemons that implement these routing protocols." msgstr "" #: ../../exercises/routing-protocols.rst:13 #, rst-text msgid "Exploring OSPF" msgstr "" #: ../../exercises/routing-protocols.rst:15 #, rst-text msgid "" "We first use IPMininet_ to explore the operation of OSPFv3, the version of " "OSPF that supports IPv6. We create a simple network with three routers and " "two hosts as shown in the figure below." msgstr "" #: ../../exercises/routing-protocols.rst:80 #, rst-text msgid "" "The code is very simple as by default IPMininet_ enables OSPF on routers. We " "introduce two specific parameters. First, the interface that connects a " "router to a host is flagged as a passive interface (``igp_passive=True``). " "This indicates to the router that there are no other routers attached to " "this interface and that it should not send or accept OSPF Hello messages on " "this interface. The second configuration parameter is that we set the IGP " "cost on each link." msgstr "" #: ../../exercises/routing-protocols.rst:83 #, rst-text msgid "" "We use this mininet_ topology to collect packet traces that show the packets " "that OSPF routers exchange. For this, we add the following ``post_build`` " "method that IPMininet_ starts after having constructed the network and " "before launching the daemons. It simply starts tcpdump_ on each router to " "collect the first 100 OSPF packets that they send/receive." msgstr "" #: ../../exercises/routing-protocols.rst:94 #, rst-text msgid "" "Finally, we can start the IPMininet_ topology and launch the daemons. The " "entire script is available from :download:`/exercises/ipmininet_scripts/" "ospf6.py`." msgstr "" #: ../../exercises/routing-protocols.rst:106 #, rst-text msgid "The script starts the routers and hosts." msgstr "" #: ../../exercises/routing-protocols.rst:120 #, rst-text msgid "" "We can easily verify that the paths used to forward packets are the expected " "ones according to the configured IGP weights." msgstr "" #: ../../exercises/routing-protocols.rst:135 #, rst-text msgid "" "We can also connect to the OSPFv3 daemon running on the routers to observe " "its state. For this, we use the ``noecho r1 telnet localhost ospf6d`` " "command." msgstr "" #: ../../exercises/routing-protocols.rst:152 #, rst-text msgid "" "The password to access this daemon is `zebra`. It supports various commands " "that are described in the `FRRouting documentation `_ We " "briefly illustrate some of them below." msgstr "" #: ../../exercises/routing-protocols.rst:175 #, rst-text msgid "" "The ``show ipv6 ospf6`` command reports the general state of the OSPFv3 " "daemon. The ``show ipv6 ospf6 neighbor`` command reports the state of the " "connected neighbors." msgstr "" #: ../../exercises/routing-protocols.rst:186 #, rst-text msgid "" "In its output, we see that ``r1`` is attached to two different routers. " "Finally, the ``show ipv6 ospf6 database`` returns the full OSPFv3 database " "with all the link state information that was distributed by OSPFv3." msgstr "" #: ../../exercises/routing-protocols.rst:239 #, rst-text msgid "" "We can also use the packet traces that were collected by tcpdump_ to observe " "the packets that the OSPFv3 daemons exchange. OSPFv3 is a more complex " "protocol that the basic link state protocol that we have described in this " "book, but you should be able to understand some of these packets. The packet " "traces are available as :download:`/exercises/traces/ospf6-r1-trace.pcap`, " ":download:`/exercises/traces/ospf6-r2-trace.pcap` and :download:`/exercises/" "traces/ospf6-r3-trace.pcap`. Here are a few interesting packets collected on " "router ``r1``." msgstr "" #: ../../exercises/routing-protocols.rst:241 #, rst-text msgid "" "The first packet that this router received his a Hello packet that was sent " "by router ``r2``. There are several interesting points to note about this " "packet. First, its source address is the link-local address " "(``fe80::68bc:b4ff:fe19:42b7``) of router ``r2`` on this interface. The " "destination address of the packet is reserved IPv6 multicast address for " "OSPFv3, i.e. ``ff02::5``. The Hop Limit of the packet is set to 1 and OSFPv3 " "uses a next header of type 89." msgstr "" #: ../../exercises/routing-protocols.rst:245 #, rst-text msgid "" "The Hello packet contains some parameters such as the `Hello interval` that " "is set to 1 second. This interval is the delay between the transmission of " "successive Hello packets. Since the `Router Dead Interval` is set to 3 " "seconds, the router will consider the link as down if it does not receive " "Hello packets during a period of 3 seconds. The second packet of the trace " "is sent by router ``r1``." msgstr "" #: ../../exercises/routing-protocols.rst:249 #, rst-text msgid "" "We can then observe the Database description packet that is sent by routers " "to announce the state of their OSPFv3 database. The details of this packet " "are beyond the scope of this simple exercise." msgstr "" #: ../../exercises/routing-protocols.rst:253 #, rst-text msgid "" "This packet is updated when new information is added in the router's OSPFv3 " "database. A few seconds router, this router sends another Database " "description packet that announces more information." msgstr "" #: ../../exercises/routing-protocols.rst:257 #, rst-text msgid "" "Router ``r2`` reacts to this updated Database description packet by " "requesting the link state information that it does not already know. For " "this, it sends a `LS Request` packet." msgstr "" #: ../../exercises/routing-protocols.rst:261 #, rst-text msgid "" "The requested information is sent in a `LS Update` packet shortly after that." msgstr "" #: ../../exercises/routing-protocols.rst:265 #, rst-text msgid "" "OSPFv3 also includes `LS Acknowledge` packets that acknowledge the correct " "reception of link state information." msgstr "" #: ../../exercises/routing-protocols.rst:269 #, rst-text msgid "" "A more detailed discussion of the packets that routing protocols exchange " "may be found in [Goralski2009]_." msgstr "" #: ../../exercises/routing-protocols.rst:272 #, rst-text msgid "Exploring RIP" msgstr "" #: ../../exercises/routing-protocols.rst:274 #, rst-text msgid "" "IPMininet_ can also be used to perform experiments with RIP. A simple script " "that uses RIPng is provided below." msgstr "" #: ../../exercises/routing-protocols.rst:336 #, rst-text msgid "" "As RIP messages are exchanged using UDP on port 521, we filter this port in " "the tcpdump_ trace. RIPng distributes the routes and our two hosts can " "exchange packets. The entire script is available from :download:`/exercises/" "ipmininet_scripts/ripng.py`." msgstr "" #: ../../exercises/routing-protocols.rst:357 #, rst-text msgid "" "We can observe the RIPng messages that are exchanged over the network. " ":rfc:`2080` defines two types of RIPng messages:" msgstr "" #: ../../exercises/routing-protocols.rst:359 #, rst-text msgid "the requests" msgstr "" #: ../../exercises/routing-protocols.rst:360 #, rst-text msgid "the responses that contain the router's routing table" msgstr "" #: ../../exercises/routing-protocols.rst:362 #, rst-text msgid "" "When a router starts, it sends a request message. This is illustrated in the " "figure below with the first message sent by router ``r2``. This message is " "sent inside an IPv6 packet whose source address is the link-local address of " "the router and the destination address is ``ff02::9`` which is the reserved " "multicast address for RIPng." msgstr "" #: ../../exercises/routing-protocols.rst:366 #, rst-text msgid "" "Router ``r2`` receives a similar request from ``fe80::481a:48ff:fed7:292e`` " "and replies by sending its routing table in a response message. Note that " "this message is sent to the link-local address of the requesting router." msgstr "" #: ../../exercises/routing-protocols.rst:370 #, rst-text msgid "" "Later, router ``r2`` will regularly transmit its distance vector inside an " "unsolicited response message that is sent towards the IPv6 multicast address " "``ff02::9``." msgstr "" #: ../../exercises/routing-protocols.rst:374 #, rst-text msgid "" "The packet traces collected on the three routers of this example are " "available from :download:`/exercises/traces/ripng-r1-trace.pcap`, " ":download:`/exercises/traces/ripng-r2-trace.pcap` and :download:`/exercises/" "traces/ripng-r3-trace.pcap`." msgstr "" #: ../../exercises/routing-protocols.rst:378 #, rst-text msgid "Exploring BGP" msgstr "" #: ../../exercises/routing-protocols.rst:380 #, rst-text msgid "" "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." msgstr "" #: ../../exercises/routing-protocols.rst:434 #, rst-text msgid "" "As in the previous examples, we create the routers and associate one IPv6 " "prefix to each AS:" msgstr "" #: ../../exercises/routing-protocols.rst:436 #, rst-text msgid "``AS1`` is assigned ``2001:cafe:1::/48``" msgstr "" #: ../../exercises/routing-protocols.rst:437 #, rst-text msgid "``AS2`` is assigned ``2001:cafe:2::/48``" msgstr "" #: ../../exercises/routing-protocols.rst:438 #, rst-text msgid "``AS3`` is assigned ``2001:cafe:3::/48``" msgstr "" #: ../../exercises/routing-protocols.rst:454 #, rst-text msgid "" "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." msgstr "" #: ../../exercises/routing-protocols.rst:491 #, rst-text msgid "" "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" msgstr "" #: ../../exercises/routing-protocols.rst:510 #, rst-text msgid "" "The script ends by launching the full topology. The entire script is " "available from :download:`/exercises/ipmininet_scripts/ebgp-simple.py`." msgstr "" #: ../../exercises/routing-protocols.rst:512 #, rst-text msgid "We can now run this simple network." msgstr "" #: ../../exercises/routing-protocols.rst:518 #, rst-text msgid "" "If you launch the script and immediately type ``ping6all`` to check the " "connectivity, you might obtained the following result." msgstr "" #: ../../exercises/routing-protocols.rst:529 #, rst-text msgid "" "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." msgstr "" #: ../../exercises/routing-protocols.rst:540 #, rst-text msgid "" "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." msgstr "" #: ../../exercises/routing-protocols.rst:542 #, rst-text msgid "We have configured the following addresses on the hosts." msgstr "" #: ../../exercises/routing-protocols.rst:559 #, rst-text msgid "" "We can now explore the routes in this small Internet. Host ``h1`` can reach " "directly host ``h3``." msgstr "" #: ../../exercises/routing-protocols.rst:569 #, rst-text msgid "Note that the path preferred by ``AS3`` to reach ``AS1`` is different." msgstr "" #: ../../exercises/routing-protocols.rst:581 #, rst-text msgid "The same applies for the paths between ``h1`` and ``h2``" msgstr "" #: ../../exercises/routing-protocols.rst:598 #, rst-text msgid "" "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." msgstr "" #: ../../exercises/routing-protocols.rst:619 #, rst-text msgid "" "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 `?`." msgstr "" #: ../../exercises/routing-protocols.rst:649 #, rst-text msgid "" "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`." msgstr "" #: ../../exercises/routing-protocols.rst:663 #, rst-text msgid "" "A useful command to start is `show bgp summary` which provides a summary of " "the state of the BGP daemon." msgstr "" #: ../../exercises/routing-protocols.rst:685 #, rst-text msgid "" "This router (`as1`) has two BGP neighbors: ``2001:cafe:1:12::2`` and " "``2001:cafe:1:13::3``. Both BGP sessions are established using the current " "version of the protocol (version 4). About 50 messages were sent/received " "over each session. These messages are mainly the BGP Keepalive messages that " "are exchanged every 30 seconds. The last column indicates that two prefixes " "were received over each session. We can see more details about these two " "eBGP sessions with the `show bgp neighbors` command." msgstr "" #: ../../exercises/routing-protocols.rst:812 #, rst-text msgid "" "We can now observe the BGP-Loc-RIB of the router with the ``show bgp ipv6 " "command`` command." msgstr "" #: ../../exercises/routing-protocols.rst:838 #, rst-text msgid "" "It is interesting to look at the output of this command in details. Router " "`as1` has routes for three different IPv6 prefixes. The first prefix is its " "own prefix, ``2001:cafe:1::/48``. It has no nexthop since this prefix is " "originated by the router. Then, `as1` has received two paths for " "``2001:cafe:2::/48``. In the BGP Loc-RIB, the `>` character indicates the " "best route according to the BGP decision process. ``2001:cafe:2::/48`` was " "learned over two different BGP sessions:" msgstr "" #: ../../exercises/routing-protocols.rst:840 #, rst-text msgid "" "the eBGP session with ``fe80::3c81:2eff:fe19:465d`` with an AS-Path of " "``AS3:AS2`` (see last column)" msgstr "" #: ../../exercises/routing-protocols.rst:841 #, rst-text msgid "" "the eBGP session with ``fe80::c001:dcff:fe49:a512`` with an AS-Path of " "``AS2`` (see last column)" msgstr "" #: ../../exercises/routing-protocols.rst:843 #, rst-text msgid "" "The first of these two routes is preferred as indicated by the `>` character " "because it has a higher ``local-preference` (150) than the second one (100). " "For prefix ``2001:cafe:3::/48``, the route learned via " "``fe80::3c81:2eff:fe19:465d`` is also preferred for the same reason." msgstr "" #: ../../exercises/routing-protocols.rst:845 #, rst-text msgid "" "IPMininet_ also allows to explore the dynamics of BGP by looking at the " "packets that the routers exchange. For this, we slightly modify the example " "above and add delays to the interdomain links as follows." msgstr "" #: ../../exercises/routing-protocols.rst:854 #, rst-text msgid "" "We also add a ``post_build`` method to launch tcpdump_ and capture the BGP " "packets exchanged by the routers. A BGP session runs over a TCP connection. " "Let us examine a few of the BGP messages exchanged on the BGP session " "between ``AS1`` and ``AS2``. The traces collected on the three routers are " "available from :download:`/exercises/traces/bgp-as1-trace.pcap`, :download:`/" "exercises/traces/bgp-as2-trace.pcap` and :download:`/exercises/traces/bgp-" "as2-trace.pcap`." msgstr "" #: ../../exercises/routing-protocols.rst:856 #, rst-text msgid "" "The BGP session starts with a TCP three-way handshake. Once the session has " "been established, both BGP daemons send an ``OPEN`` message describing their " "capabilities and the BGP extensions that it supports. The details of these " "extensions go beyond the scope of this book. However, it is important to " "note that the ``OPEN`` message contains the ``AS`` number of the router that " "sends the message and its identifier as a 32 bits IPv4 address. This router " "identifier uniquely identifies the router. The last mandatory parameter of " "the ``OPEN`` message is the `Hold Time`, i.e. the maximum delay between two " "successive messages over this BGP session. A BGP router should send " "``KEEPALIVE`` messages every one third of the `Hold Time` to keep the " "session up." msgstr "" #: ../../exercises/routing-protocols.rst:861 #, rst-text msgid "" "The ``UPDATE`` message can be used to withdraw and advertise routes. The " "packet below is sent by ``AS2`` to advertise its route towards " "`2001:cafe:2::/48` on the BGP session with ``AS1``." msgstr "" #: ../../exercises/routing-protocols.rst:866 #, rst-text msgid "" "Another interesting utilization of IPMininet_ is to explore how routers " "react to link failures. We start from the same network as with the previous " "example and disable the link between ``AS2`` and ``AS3``. For this, we log " "on one of the two routers and issue the following commands." msgstr "" #: ../../exercises/routing-protocols.rst:898 #, rst-text msgid "" "We first connect to the BGP daemon on router `as2`. In addition to the `show`" " commands that have been described earlier, the router also supports " "privileged commands that can change its configuration. Before executing " "these commands, we must enter the privileged mode with the `enable` command. " "On production routers, this command requires a password to verify the " "credentials of the network administrator. The `#` prompt indicates that we " "are allowed to execute privileged commands. We first check the state of the " "BGP sessions with the `show bgp summary` commands. There are two BGP " "sessions configured on this router." msgstr "" #: ../../exercises/routing-protocols.rst:900 #, rst-text msgid "We can now disable one of the BGP sessions on router `as2` as follows." msgstr "" #: ../../exercises/routing-protocols.rst:911 #, rst-text msgid "" "We start indicate that we will use the terminal to change the router " "configuration with `configure terminal`. We then enter the BGP part of the " "configuration with `router bgp 2` (`2` is the AS number of `as2`). Then we " "use the `neighbor 2001:cafe:2:23::3 shutdown` that takes as parameter the IP " "address of the peer of the session that we want to stop. We then leave the " "BGP part of the configuration (first `exit`) and the configuration menu " "(second `exit` command). At this point, the BGP session between ``AS2`` and " "``AS3`` is down." msgstr "" #: ../../exercises/routing-protocols.rst:930 #, rst-text msgid "" "Without a BGP session between ``AS2`` and ``AS3``, there are reachability " "problems in this simple Internet." msgstr "" #: ../../exercises/routing-protocols.rst:941 #, rst-text msgid "" "We can fix them by enabling again the BGP session with the `no neighbor " "2001:cafe:2:23::3 shutdown` command." msgstr "" #: ../../exercises/routing-protocols.rst:989 #, rst-text msgid "Exercises" msgstr "" #: ../../exercises/routing-protocols.rst:991 #, rst-text msgid "" "We can use IPMininet_ to prepare some networks with problems that need to be " "analyzed and corrected." msgstr "" #: ../../exercises/routing-protocols.rst:993 #, rst-text msgid "" "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`." msgstr "" #: ../../exercises/routing-protocols.rst:1016 #, rst-text msgid "" "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" msgstr "" #: ../../exercises/routing-protocols.rst:1029 #, rst-text msgid "" "Another interesting utilization IPMininet_ is to explore the impact of a " "link failure. We start from a small variant of the above topology." msgstr "" #: ../../exercises/routing-protocols.rst:1052 #, rst-text msgid "When this network starts, all hosts can reach all other hosts." msgstr "" #: ../../exercises/routing-protocols.rst:1066 #, rst-text msgid "" "Draw the network and try to predict how it will react to a shutdown of any " "of the customer-provider links ?" msgstr "" #: ../../exercises/routing-protocols.rst:1068 #, rst-text msgid "" "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 ?" msgstr "" #: ../../exercises/routing-protocols.rst:1098 #, rst-text msgid "" "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 ?" msgstr "" #: ../../exercises/routing-protocols.rst:1128 #, rst-text msgid "" "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 ?" msgstr "" #: ../../exercises/routing-protocols.rst:1158 #, rst-text msgid "" "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 ?" msgstr "" #: ../../exercises/routing-protocols.rst:1190 #, rst-text msgid "" "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`." msgstr "" #: ../../exercises/routing-protocols.rst:1228 #, rst-text msgid "" "What is the Loc-RIB of ``AS6`` for prefix `p9` ? Indicate which is the best " "route towards this prefix." msgstr "" #: ../../exercises/routing-protocols.rst:1230 #, rst-text msgid "" "What is the Loc-RIB of ``AS9`` for prefix `p2` ? Indicate which is the best " "route towards this prefix." msgstr "" #: ../../exercises/routing-protocols.rst:1232 #, rst-text msgid "" "The network below contains nine ASes with one host per AS. Assuming that " "``AS1`` announces prefix `p1` and that ``AS2`` announces prefix `p2`." msgstr "" #: ../../exercises/routing-protocols.rst:1265 #, rst-text msgid "" "What is the Loc-RIB of ``AS6`` for prefix `p1` ? Indicate which is the best " "route towards this prefix." msgstr "" #: ../../exercises/routing-protocols.rst:1267 #, rst-text msgid "" "What is the Loc-RIB of ``AS8`` for prefix `p2` ? Indicate which is the best " "route towards this prefix." msgstr "" #: ../../exercises/routing-protocols.rst:1272 #, rst-text msgid "" "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`." msgstr "" #: ../../exercises/routing-protocols.rst:1312 #, rst-text msgid "" "The network does not provide a full connectivity. The hosts attached to " "``AS5`` cannot ping the hosts attached to ``AS8``." msgstr "" #: ../../exercises/routing-protocols.rst:1327 #, rst-text msgid "" "What is the path that packets follow from a host attached to ``AS1`` to a " "host attached to ``AS8`` ?" msgstr "" #: ../../exercises/routing-protocols.rst:1339 #, rst-text msgid "" "What is the path that packets follow from a host attached to ``AS8`` to a " "host attached to ``AS1`` ?" msgstr "" #: ../../exercises/routing-protocols.rst:1351 #, rst-text msgid "" "What is the path that packets follow from a host attached to ``AS8`` to a " "host attached to ``AS2`` ?" msgstr "" #: ../../exercises/routing-protocols.rst:1364 #, rst-text msgid "" "What is the path that packets follow from a host attached to ``AS2`` to a " "host attached to ``AS7`` ?" msgstr "" #: ../../exercises/routing-protocols.rst:1375 #, rst-text msgid "" "We now disable the interdomain link between ``AS3`` and ``AS4``. What are " "the hosts that ``AS1``, ``AS5`` and ``AS6`` are still able to ping ?" msgstr ""