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CCNA Flashes I.02 (Network Devices & Topologies)

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What are two types of Layer 1 network devices?
Two types of Layer 1 network devices are: - Repeaters: Repeaters regenerate and retime network signals, amplifying them, which allows the signal to travel a longer distance on a network medium. - Hubs: A hub is also known as a multiple-port repeater. It also regenerates and retimes network signals. The main difference between a hub and a repeater is the number of cables that connect to the device. A repeater typically has two ports, whereas a hub has from four to 48 ports.
What are some network devices that operate at the data link layer (Layer 2)?
Bridges and switches are network devices that operate at the data link layer. Both devices decide what traffic to forward or drop (filter) based on MAC addresses. Logical network addresses are not used at this layer. Data link layer devices assume a flat address space. Typically, a bridge is designed to create two or more LAN segments and is usually implemented in software. A switch is a high-speed multiport bridge that is typically implemented in hardware. Switches are designed to replace hubs while providing the filtering benefits of bridges.
What are collision domains?
A collision domain defines a group of devices connected to the same physical medium. A collision occurs when two packets are sent at the same time and collide with each other (electronically). When a collision occurs, a jam signal is sent by the workstation detecting the collision to clear the segment. A jam signal affects all the machines on the segment, not just the two that collided; when the jam signal is on the wire, no workstations can transmit data. The more collisions that occur in a network, the slower it is, because the devices have to resend the packet.
What devices are used to break up collision domains?
Switches, bridges, and routers are used to break up collision domains. They create more collision domains and fewer collisions. Each port on a bridge, switch, and router creates one collision domain. For example, a switch with 24 ports has 24 separate collision domains.
At what layer of the OSI model do routers and multilayer switches function?
Routers and some multilayer switches function at the network layer (Layer 3) of the OSI model. Both devices learn, record, and maintain awareness of different networks. They decide the best path to these networks and maintain the following information in a routing table: - Protocol-specific network addresses. If you run more than one protocol, each one has a network address. - The interface the router uses to route a packet to a different network. - A metric, which is the distance to a remote network or the weight of the bandwidth, load, delay, and path's reliability to the remote network.
What three pieces of info are found in a routing table?
a) Protocol-specific network addresses. If you run more than one protocol, each one has a network address. - b) The interface the router uses to route a packet to a different network. - c) A metric, which is the distance to a remote network or the weight of the bandwidth, load, delay, and path's reliability to the remote network.
One interface on a router creates how many broadcast and how many collision domains?
1,1
One interface on a switch creates how many broadcast and how many collision domains?
0,1
In addition to learning the remote network and providing a path to the network, what seven other functions do routers carry out?
Routers perform these tasks: - 1) By default, they do not forward broadcasts or multicasts. - 2) Routers can perform bridging, encapsulation, and routing functions. - 3) If a router has multiple paths to a destination, it can determine the best path to the destination. - 4) Routers forward traffic based on Layer 3 destination addresses. - 5) Routers can connect virtual LANs (VLANs) by routing traffic between them. - 6) Routers can provide quality of service for specified types of network traffic. - 7) Routers provide security, packet filtering, and address translation.
Does a router forward broadcasts or multicasts?
No
Can routers connect virtual LANs (VLANs) by routing traffic between them.
Yes
Can routers provide QoS for specified types of network traffic?
Yes
What are broadcast domains?
A broadcast domain defines a group of devices that receive each others' broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower the network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.
What devices are used to break up broadcast domains?
Routers are used to break up broadcast domains. They create more broadcast domains and smaller broadcast areas.
Is there any circumstance under which a switch could create a broadcast domain?
Yes, with a VLAN created on a switch.
Describe the difference between a physical network topology and a logical network topology.
All of today's networks have physical and logical topologies. Physical topologies refer to the physical layout of devices and network media. Logical topologies refer to the logical paths in which data accesses the medium and transmits packets across it.
What are the five types of physical topologies implemented in today's networks?
The five most common physical network topologies implemented today are: - Bus - Ring - Star - Extended star - Mesh
What physical network topology connects all devices to one cable?
A bus & ring topology connects all devices by a single cable. This cable connects from one computer to another. In a logical bus and a single ring topology, only one packet can be sent at a time.
Describe a star and extended star physical topology.
A star or extended star physical topology is made up of a central connection point, such as a hub or switch, where all cable segments connect. A star topology resembles spokes in a wheel. It is the network topology of choice in Ethernet networks. When a star network is expanded to include additional network devices that connect to a main center network device, it is called an extended star topology.
Describe a ring topology.
In a ring topology, all hosts and devices are connected in a ring or circle. There are two types of ring networks: - Single-ring: In a single-ring network, all devices share a single cable, and data travels in one direction. Each device waits its turn to send data over the network. - Dual-ring: A dual-ring network has a second ring to add redundancy and allows data to be sent in both directions.
What physical network topology connects all devices to each other?
A mesh network connects all devices to each other for fault tolerance and redundancy.

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