Exam Essentials

Remember the advantages of segmenting your LAN with switches. Know that most network congestion problems are related to too many hosts on a particular network segment. Switches provide for the segmentation of hosts and a less congested network design.

Know the reasons to segment your LAN with bridges. Bridges are an earlier form of a switch with fewer ports to segment groups of hosts instead of individual hosts, but they still provide the segmentation for a less congested network design.

Understand the placement of routers in your network design. Routers operate at the Network layer and control network broadcasts. A properly routed network creates a more efficient design and less network traffic at each NIC or device.

Understand the difference between a Layer 2 switch and a Layer 3 switch. The Layer 2 (L2) switch makes forward/filter decisions based on hardware (MAC) address. The Layer 3 (L3) switch uses a route processor if packets are forwarded to another remote network.

Understand the advantages of using a Layer 3 backbone over a Layer 2 backbone. By using a Layer 3 backbone you can reduce the number of connections between switches and scale to a large size all while keeping your broadcasts under control.

Remember the three LAN switch methods and the benefits of each. The three LAN switch methods are cut-through, store-and-forward, and FragmentFree. Cut-through switching waits for the destination hardware address only before forwarding the frame (low latency). Store-and-forward switching waits for the entire frame. A CRC is run, and then the switch finds the destination port in the MAC filter table and forwards the frame (high latency, fewer errors). FragmentFree switching (also known as modified cut-through) checks the first 64 bytes for fragmentation and then forwards the frame.

Know the differences between half-duplex and full-duplex Ethernet. When network devices are configured for half-duplex Ethernet, a single line is used to tie the devices together, causing them to share their send and receive times. When devices are configured for full-duplex Ethernet, they can send and receive simultaneously using parallel lines.

Understand the operation and benefits of the Spanning-Tree Protocol. The Spanning-Tree Protocol (STP) uses the spanning-tree algorithm (STA) to find redundant paths to a root bridge or switch and to eliminate the loops between two or more network segments.