English
Without a BGP session between ``AS2`` and ``AS3``, there are reachability problems in this simple Internet.
When this network starts, all hosts can reach all other hosts.
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
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.
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 ``AS8`` to a host attached to ``AS1`` ?
What is the path that packets follow from a host attached to ``AS2`` to a host attached to ``AS7`` ?
What is the path that packets follow from a host attached to ``AS1`` to a host attached to ``AS8`` ?
What is the Loc-RIB of ``AS9`` for prefix `p2` ? 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.
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 ``AS6`` for prefix `p1` ? Indicate which is the best route towards this prefix.
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 ?
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 ``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 ``AS2`` fails ? How does this affect the reachability of the different hosts ?
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.
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.
We now disable the interdomain link between ``AS3`` and ``AS4``. What are the hosts that ``AS1``, ``AS5`` and ``AS6`` are still able to ping ?
We have configured the following addresses on the hosts.