CCDA 640-864 Official Cert Guide - Chapter 3 Summary

Enterprise Campus:

LAN Media: by IEEE 802.3

Physical Terminations

LAN Hardware:

Repeaters, HUB, Bridge, Switch, Router, L3 Switch.

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.

An Ethernet hub, active hub, network hub, repeater hub or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. A hub works at the physical layer (layer 1) of the OSI model. The device is a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision. The difference is that hubs have more ports than basic repeaters.

A network bridge connects multiple network segments at the data link layer (Layer 2) of the OSI model. In Ethernet networks, the term bridge formally means a device that behaves according to the IEEE 802.1D standard. A bridge and a switch are very much alike; a switch being a bridge with numerous ports. Switch or Layer 2 switch is often used interchangeably with bridge.

A router is a device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it gets to its destination node.

Within the confines of the Ethernet physical layer, a layer 3 switch can perform some or all of the functions normally performed by a router. The most common layer-3 capability is awareness of IP multicast through IGMP snooping.

Inter-Switch Link and IEEE 802.1Q Frame Format:

Inter-Switch Link and IEEE 802.1Q Frame Format

RPVST+

Understanding Rapid Spanning Tree Protocol (802.1w)

CGMP

Cisco Group Management Protocol is a Cisco proprietary protocol implemented to control multicast traffic at Layer 2. Because a Layer 2 switch is unaware of Layer 3 IGMP messages, it cannot keep multicast packets from being sent to all ports. You must also enable the router to speak CGMP with the LAN switches. With CGMP, switches distribute multicast sessions to the switch ports that have group members.

http://abnouri.free.fr/techmodule/doc_img/CGMP.swf

IGMP Snooping

IGMP snooping is the process of listening to Internet Group Management Protocol (IGMP) network traffic. IGMP snooping, as implied by the name, is a feature that allows a network switch to listen in on the IGMP conversation between hosts and routers. By listening to these conversations the switch maintains a map of which links need which IP multicast streams. Multicasts may be filtered from the links which do not need them.