Reading
Cisco Ethernet Overview Ethernet Switch Tutorial
Linux Bridging
Understanding the Spanning Tree Protocol
Configuring Spanning Trees
Tasks
The focus of this lab is on local area networks. Local area networks
enable end hosts to communicate, and for end hosts to connect to Internet
uplinks. While many different LAN technologies and protocols have been
developed over the years, Ethernet is the most widely used today, and is
the focus of this lab. Note that communications in local area networks
takes place at layer 2 (data link) of the protocol stack and is therefore
concerned with Medium Access Control (MAC) and MAC addresses as opposed to
layer 3 (network) and IP addresses which will be the subject of lab #4.
You will gain experience with LANs by conducting two different experiments
in this lab. The first will be to create a LAN bridge using a Linux
host. This portion of the lab will require that you become familiar with
the brctl tool which interacts with the bridge kernel module available
in the standard linux kernel. In the lab, you will configure a Linux host
to act as a communications bridge between two hosts.
While bridging is important in terms of enabling multiple LANs to be
connected, LAN switching is the dominate mechanism for LANs.
Switches enable on-to-one communication between end hosts, obviating the
need for traditional shared medium access methods. Furthermore, modern
switch devices offer a host of configuration and management capabilities
that enable devices to be tuned for specific environments. The second part
of this lab will give you an introduction to LAN switching and require you
to configure and test a commonly used switch in several different ways.
Tools
In addition to the recommended readings above, you will need to familiarize
yourself with the brctl utility that is available in Linux. Use the
Linux MAN pages to learn the syntax details of this utility.
Topology
You will build a network that has the following topology in the first half
of this lab:
Questions
Please enter the answers to these questions into your lab notebooks before you
start the lab.
1. How does Ethernet implement multiple access on a shared
bus?
2. Explain the difference between a switch and a hub. When
would one be preferable over another?
3. What is an Ethernet collision domain and why is it an
important consideration in Ethernet LAN design?
4. How is the Spanning Tree Algorithm used in LANs?
5. What is a forwarding loop? How does it occur?
6. Design a topology of 5 switches/bridges that would cause
a forwarding loop. Draw this topology in your lab notebook
and explain where the loop would occur.
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