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Network switching upgrade for star (hub & spoke) topology

You are the IT manager of an Elementary School. The school is adding computers that have been donated by a local company. An extended star topology has been suggested, using some hubs that are available. The school agrees with your idea of adding a switch working as a backbone switch, as shown in the figure below. The plan is to replace the classroom hubs as the budget allows.

For now, the very basic details are as follows: the Elementary School is a four-year-old, single-level building with 12 classrooms and a library. Each classroom currently has 24 students but could possibly seat 32 students. There are currently no portable classrooms but a student enrollment growth is just starting to hit the school.

Enough computers are available for six classrooms and the library immediately, and the intent is to outfit the remaining six classrooms next year. The plan is to make the Internet and some online services available to the students. The computers are current enough to be useful for at least two years.

The library, which is somewhat centrally located, is where the server(s) and router connecting the school to the Internet will be located. Assume that all rooms will have 24 computers and that each room will use a stackable hub solution that combines a 12-port hub and a 24-port hub for 36 total ports. Being stackable units, the network will see each stack as a single 36-port device.

1. Review the above room requirements to conclude what type of network media is most appropriate for this situation?

2. How many IP addresses does the school need immediately? How many might it eventually need for the initial seven rooms? How many could it need if it gets enough computers for the entire school? Exact numbers aren't expected, but you should be able to estimate pretty close from the data provided.

3. What class(es) of IP address do you need now and in the future?

4. The school district informs the group that it can afford 2 public IP addresses for the Internet access. Is this a problem if the school wants all the computers to access the Internet? Explain why or why not.

5. Visit the Library and look up links to find the prices of routers, cable, and switches. In some sites, you may have to choose Networking on the site's main page to get started. If you aren't familiar with manufacturers, try Cisco, 3Com, Novell, D-Link, and Linksys.

Solution Preview

1. Assuming the centrally-located library is within 100 meters to each of the 12 classrooms, Ethernet would be the most affordable and most appropriate network media for the school to connect its switch to the rooms' hubs. Category (Cat) 6 or 5/5e cable can be used to provide 100 Mbps or 1 Gbps speeds between the library's switch and each room's two hubs (one 12-port and one 24-port).

If any classroom is farther than 100 meters (http://en.wikipedia.org/wiki/Ethernet_physical_layer) from the library, then an Ethernet extender device will be required at a minimum, or some type of fiber infrastructure would need to be considered, depending on the interfaces available on the switch and hubs. This Ethernet cabling can stay in place as the hubs gradually get upgraded to switches in the future.

2. As of today, with no Internet access, one central switch, and hubs at each of the 12 classrooms, no IP addresses are needed immediately. The network is a huge layer-2 network with communication conducted through MAC addresses. Going forward, if Internet services are added, then each ISP (Internet Service Provider) will assign one public IP address to the router (see answer to #4).

As the hubs get replaced by switches, we will need to allocate IP addresses to both the switches and the endpoint computers. With this scenario, we architect the library's central switch as the distribution backbone switch, and the 13 downlink switches in the rooms as access switches. Between each pair of ...

Solution Summary

This solution covers a network upgrade for an elementary school's current hubs to layer 2 switches. IP addressing, subnets/classes, and vendors' hardware are also discussed.

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