You are a networking professional who works in a college computer lab. The computers run only the TCP/IP protocol on an Ethernet network, and all computers use 3Com NICs. Many beginning CIT students use this lab for homework; you help them access the network and troubleshoot problems with their connections on a daily basis. One day, a student begins tampering with his computer; when he restarts the computer, it alerts him that it can't find the network. He calls you over to help. You ensure all the physical connections are sound. Then, you check the workstation's network properties and find that he has changed the frame type that his NIC uses to transmit data from Ethernet to token ring. Explain why this has prevented the workstation from connecting to the network.

Frames are composed of several smaller components or fields. The characteristics of these components depend on the type of network on which the frames run and on the standards that they must follow. In our case all the lab computers run only the TCP/IP protocol on the Ethernet network and all the computers use 3Com NICs.

Actually, this is very good and valuable information because as we know some manufacturers have several different OUIs (Organizationally Unique Identifier). In this particular case 3Com Corporation uses its own OUI and standards for their NICs. Ethernet frames are different from token ring frames and the two will not interact with each other on a network.

Although we can conceivably transmit both token ring and Ethernet frames on a network, Ethernet interfaces cannot interpret token ring frames and vice versa. By changing the frame type (in our case student changed it) which workstation's NIC was using to transmit data from Ethernet to token ring, obviously the connection between these two networking technologies was gone.

I would explain to students that this kind of changes in network settings is not recommended and restricted in the lab. I imposed such restrictions because of safety and security reasons and to protect the network settings. It is very important to know what frame type or types each network require.

This information is very useful for installing network operating systems, configuring servers and client workstations, installing NICs, troubleshooting network problems and purchasing network equipment.