cnp3-ebook/exercises/routing-protocols

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13 ../../exercises/routing-protocols.rst:186

	English 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. 214/10000 · 214
14 ../../exercises/routing-protocols.rst:239

	English 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``. 542/10000 · 542
15 ../../exercises/routing-protocols.rst:241

	English 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. 462/10000 · 462
16 ../../exercises/routing-protocols.rst:245

	English 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``. 396/10000 · 396
17 ../../exercises/routing-protocols.rst:249

	English 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. 196/10000 · 196
18 ../../exercises/routing-protocols.rst:253

	English 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. 194/10000 · 194
19 ../../exercises/routing-protocols.rst:257

	English 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. 178/10000 · 178
20 ../../exercises/routing-protocols.rst:261

	English The requested information is sent in a `LS Update` packet shortly after that. 77/10000 · 77
21 ../../exercises/routing-protocols.rst:265

	English OSPFv3 also includes `LS Acknowledge` packets that acknowledge the correct reception of link state information. 111/10000 · 111
22 ../../exercises/routing-protocols.rst:269

	English A more detailed discussion of the packets that routing protocols exchange may be found in [Goralski2009]_. 106/10000 · 106
23 ../../exercises/routing-protocols.rst:272

	English Exploring RIP 13/10000 · 13
24 ../../exercises/routing-protocols.rst:274

	English IPMininet_ can also be used to perform experiments with RIP. A simple script that uses RIPng is provided below. 111/10000 · 111
25 ../../exercises/routing-protocols.rst:336

	English 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`. 251/10000 · 251
26 ../../exercises/routing-protocols.rst:357

	English We can observe the RIPng messages that are exchanged over the network. :rfc:`2080` defines two types of RIPng messages: 119/10000 · 119
27 ../../exercises/routing-protocols.rst:359

	English the requests 12/10000 · 12
28 ../../exercises/routing-protocols.rst:360

	English the responses that contain the router's routing table 53/10000 · 53
29 ../../exercises/routing-protocols.rst:362

	English 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. 333/10000 · 333
30 ../../exercises/routing-protocols.rst:366

	English 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. 222/10000 · 222
31 ../../exercises/routing-protocols.rst:370

	English Later, router ``r2`` will regularly transmit its distance vector inside an unsolicited response message that is sent towards the IPv6 multicast address ``ff02::9``. 164/10000 · 164
32 ../../exercises/routing-protocols.rst:374

	English 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`. 239/10000 · 239

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