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IPv6 Networks
Basic questions on IPv6 Networks
Before starting to determine the paths that packets will follow in an IPv6 network, it is important to remember how to convert IPv6 addresses in binary numbers.
An IPv6 forwarding table contains a list of IPv6 prefixes with their associated nexthop or outgoing interface. When an IPv6 router receives a packet, it forwards it according to its forwarding table. Note that IPv6 routers forward packets along the *longest match* between the destination address of the packet and the routes in the forwarding table.
Now that you master the basics, you can determine the paths followed by IPv6 packets in simple networks.
Design questions
Consider the network shown in the figure below. In this network, the following addresses are used.
host ``A`` : ``2001:db8:1341:1::A`` and its default route points to ``2001:db8:1341:1::1``
host ``B`` : ``2001:db8:1341:4::B`` and its default route points to ``2001:db8:1341:4::4``
The routers have one address inside each network :
router ``R1`` uses address ``2001:db8:1341:1::1`` on its West interface, address ``2001:db8:1341:12::1`` on its East interface and address ``2001:db8:1341:13::1`` on its South interface
router ``R2`` uses address ``2001:db8:1341:12::2`` on its West interface, address ``2001:db8:1341:23::2`` on its South-West interface and address ``2001:db8:1341:24::2`` on its South interface.
router ``R3`` uses address ``2001:db8:1341:34::3`` on its East interface, address ``2001:db8:1341:23::3`` on its North-East interface and address ``2001:db8:1341:13::3`` on its North interface
router ``R4`` uses address ``2001:db8:1341:34::4`` on its West interface, address ``2001:db8:1341:24::4`` on its North interface and address ``2001:db8:1341:4::4`` on its East interface
The forwarding paths used in a network depend on the forwarding tables installed in the network nodes. Sometimes, these forwarding tables must be configured manually.
In this network, propose the forwarding tables of ``R2`` and ``R3`` that ensure that hosts ``A`` and ``B`` can exchange packets in both directions.
Consider the same network as in the previous question, but now the forwarding tables of ``R2`` and ``R3`` are configured as shown below :
In this network, select `all` the rules in the shown forwarding tables that ensure that the packets sent from ``A`` to ``B`` follow the reverse path of the packets sent by ``B`` to ``A``.
router ``R2`` uses address ``2001:db8:1341:12::2`` on its West interface, and address ``2001:db8:1341:24::2`` on its South interface
router ``R3`` uses address ``2001:db8:1341:34::3`` on its East interface and address ``2001:db8:1341:13::3`` on its North interface
Routers ``R2`` and ``R3`` are buggy in this network. Besides the routes for their local interfaces (not shown in the figure), they only have a default route which is shown in the figure below.
How do you configure the forwarding tables on ``R1`` and ``R4`` so that ``A`` can reach ``B`` and the reverse ?
Consider a slightly different network than in the previous question.
Assuming that the following IPv6 addresses are used :
router ``R1`` uses address ``2001:db8:1341:1::1`` on its West interface, address ``2001:db8:1341:12::1`` on its East interface, address ``2001:db8:1341:14::1`` on its South-East interface and address ``2001:db8:1341:13::1`` on its South interface
router ``R4`` uses address ``2001:db8:1341:34::4`` on its West interface, address ``2001:db8:1341:24::4`` on its North interface, address ``2001:db8:1341:14::4`` on its North-West interface and address ``2001:db8:1341:4::4`` on its East interface
Can you configure the forwarding tables so that the following paths are used by packets sent by host ``A`` to reach one of the four addresses of router ``R4``?
Do your forwarding tables impose the path used to reach host ``B`` which is attached to router ``R4`` or do you need to configure an additional entry in these tables ?
Consider the network below that contains only routers. This network has been configured by a group of students and you must verify whether the configuration is correct. All the IPv6 addresses are part of the same ``/48`` prefix that we name ``p``. The following subnets are defined in this ``/48`` prefix.
``p:12/64`` for the link between ``R1`` and ``R2``. On this subnet, ``R1`` uses address ``p:12::1`` while router ``R2`` uses address ``p:12::2``
``p:13/64`` for the link between ``R1`` and ``R3``. On this subnet, ``R1`` uses address ``p:13::1`` while router ``R3`` uses address ``p:13::3``

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../../exercises/ipv6.rst:91
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locale/pot/exercises/ipv6.pot, string 16