Exam Essential: Internetworking

Know the possible causes of LAN traffic congestion
Too many hosts in a broadcast domain/storms, multicasting, and low bandwidth are all possible suspects of LAN traffic congestion.

Be able to distinguish the difference between a collision domain and a broadcast domain
Collision domain is an Ethernet term used to describe a network collection of devices in which one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. On a broadcast domain, a set of all devices on a network segment hear all broadcasts sent on that segment.

Be able to distinguish the difference between a hub, a bridge, a switch, and a router
Hubs create one collision domain and one broadcast domain. Bridges break up collision domains but create one super duper large broadcast domain through use of hardware addresses to filter the network. Switches are really just multiple port bridges with more intelligence. They break up collision domains but create one large broadcast domain by default and also uses hardware addresses to filter the network. Routers break up broadcast domains (as well as collision domains) and use logical addressing to filter the network.

Know the OSI layers
It’s mandatory that you know the OSI layers and the function each layer provides. There are seven layers in the OSI reference model. The upper layers consist of The Application, Presentation, and Session Layers, and are responsible for communicating from a user interface to an application. The bottom layers consist of The Transport, Network, Data Link, and Physical Layers. The transport layer provides for segmentation, sequencing, and virtual circuits. The network layer provides for framing and placing of data on the network medium. Last but not least, the physical layer is responsible for taking 1s and 0s and encoding them into a digital signal for transmission on the network segment.

Remember the types of Ethernet cabling and when to use them
There are three types of cables that can be created from an Ethernet cable:

• Straight-through
• to connect a PC’s or a router’s Ethernet interface to a hub or switch.
• Crossover
• to connect hub to hub, hub to switch, switch to switch, or PC to PC.
• Rolled
• for a console connection from a PC to a router or switch

Understand how to connect a console cable from a PC to a router and commence HyperTerminal
You should know how to do this for the exam: Take a rolled cable and connect it from the COM port of the host to the console port of a router. Start HyperTerminal and set the BPS to 9600 and flow control to none.

Memorize the three layers in the Cisco three-layer model

• Core
• Distribution
• Access