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	English
	By using :manpage:`brtcl(8)`, we can easily observe the state of the Spanning Tree protocol on the different switches. Let us start with ``s3``, i.e. the root of the Spanning Tree.
	Consider the network depicted in Fig. 5. Both of the hosts `H0` and `H1` have two interfaces: one connected to the switch `S0` and the other one to the switch `S1`. Will the link between `S0` and `S1` ever be used? If so, under which assumptions? Provide a comprehensive answer.
	Consider the switched network shown in Fig. 1. In this network, assume that the LAN between switches S3 and S12 fails. How should the switches update their port/address tables after the link failure ?
	Consider the switched network shown in Fig. 1. What is the spanning tree that will be computed by 802.1d in this network assuming that all links have a unit cost ? Indicate the state of each port.
	Consider the switched network shown in the figure below. Compute the Spanning Tree of this network.
	Exercises
	Fig. 1. A small network composed of Ethernet switches
	Fig. 2. A typical enterprise backbone network
	Fig. 3. Host `H0` performs a traceroute towards its peer `H1` through a network composed of switches and routers
	Fig. 4. Can `H0` and `H1` communicate ?
	Fig. 5. Will the link between `S0` and `S1` ever be used?
	In the network depicted in Fig. 3, the host `H0` performs a traceroute toward its peer `H1` (designated by its name) through a network composed of switches and routers. Explain precisely the frames, packets, and segments exchanged since the network was turned on. You may assign addresses if you need to.
	In the network represented in Fig. 4, can the host `H0` communicate with `H1` and vice-versa? Explain. Add whatever you need in the network to allow them to communicate.
	IPMininet_ can also be used to configure the Spanning Tree protocol on Linux hosts that act as Ethernet switches. Let us consider the simple Ethernet network shown in the figure below.
	Local Area Networks: The Spanning Tree Protocol and Virtual LANs
	:manpage:`brctl(8)` also maintains a MAC address table that contains the Ethernet addresses that have been learned on each switch port.
	Many enterprise networks are organized with a set of backbone devices interconnected by using a full mesh of links as shown in Fig.2. In this network, what are the benefits and drawbacks of using Ethernet switches and IP routers running OSPF ?
	Most commercial Ethernet switches are able to run the Spanning tree protocol independently on each VLAN. What are the benefits of using per-VLAN spanning trees ?
	Testing the Spanning Tree with IPMininet
	Thanks to the traces collected by tcpdump_, we can easily analyze the messages exchanged by the switches. Here is the fist message sent by switch ``s3``.