CCNA Tutorials

CCNA tutorials Part 1
Introduction to networking devices

HUB

Hubs connect computers together in a star topology network. Due to their design, they increase the chances for collisions. Hubs operate in the physical layer  of the OSI model and have no intelligence. Hubs flood incoming packets to all ports all the time. For this reason, if a network is connected using hubs, the chances of a collision increases linearly with the number of computers (assuming equal bandwidth use). Hubs pose a security risk since all packets are flooded to all ports all the time. If a user has packet sniffing software, they can extract data from the network and potentially decode it and use it. Hubs make it easy to "spy" on users on the same LAN as you.

REPEATER

A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation. Because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on the physical Layer, the first layer of the OSI model. Repeaters are majorly employed in long distance transmission to reduce the effect of attenuation. It is important to note that repeaters do not amplify the original signal but simply regenerate it.

What is WEP Wireless Encryption?

Wired Equivalent Privacy (WEP) is a security protocol for wireless networks that encrypts transmitted data . The disadvantage is that without any security, your data can be intercepted without difficulty.

However, WEP was an early attempt to secure wireless networks, and better security is now available such as DES, VPN, and WPA. 

WEP has three settings: Off (no security), 64-bit (weak security), 128-bit (a bit better security). WEP is not difficult to crack, and using it reduces performance slightly.

If you run a network with only the default security, where WEP is turned off, any of your neighbors can immediately log on to your network and use your Internet connection.

• For wireless devices to communicate, all of them must use the same WEP setting. (40-bit and 64-bit WEP encryption are the same thing — 40-bit devices can communicate with 64-bit devices.)

While there is no extra performance cost to encrypting the longer key, there is a cost to transmitting the extra data over the network. 128-bit security is not much more difficult than 64-bit to crack, so if you are concerned about performance, consider using 64-bit. If you're very concerned about security, use WPA, which replaces WEP which is almost impossible to crack. 

The WEP concept of passphrase is introduced so that you do not have to enter complicated strings for keys by hand. The passphrase you enter is converted into complicated keys. Choose passphrases with the same care you would important passwords.

• With 128-bit encryption, you need to enter a passphrase to generate each key.
• All four keys must be specified, because WEP switches between them to make your traffic more difficult to break.
• All devices within your LAN must use the same passphrases (i.e., the same keys).

WEP is not necessary if you have a gaming console such as PlayStation or Xbox, and there are no other computers on the network, and no neighbours nearby within wireless range.

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