Chapter 4 - Switched Networks
Cisco Borderless Network
The __________ is a network architecture that combines several innovations and design considerations to allow organizations to connect anyone, anywhere, anytime, and on any device securely, reliably, and seamlessly. The user is not aware.
The three critical layers within these tiered designs are the
access, where users try to connect distribution, -brains, firewall, servers, and core layers - backbone, fast as possible. barebones
What is a basic function of the Cisco Borderless Architecture distribution layer?
aggregating Layer 3 routing boundaries One of the basic functions of the distribution layer of the Cisco Borderless Architecture is to perform routing between different VLANs. Acting as a backbone and aggregating campus blocks are functions of the core layer. Providing access to end user devices is a function of the access layer.
What is one function of a Layer 2 switch?
determines which interface is used to forward a frame based on the destination MAC address
Fixed Configuration Switches
do not support features or options beyond those that originally came with the switch. Not able to make it look like one logical device
cut-through method switching
forwards the frame before t is entirely received. at a minimum, the destination address of the frame must be read before the frame can be forwarded. Rapid Frame Forwarding
What two criteria are used by a Cisco LAN switch to decide how to forward Ethernet frames? (
ingress port, destination MAC address
fragment-free switching
modified form of cut-through switching in which the switch waits for the collision window (64 bytes) to pass before forwarding the frame. This means each frame will be checked into the data field to make sure no fragmentation has occurred.
What are two advantages of modular switches over fixed-configuration switches?
need for fewer power outlets increased scalability
Store and Forward Switching
receives the entire frame, and computes the CRC. If the CRC is valid, the switch looks up the destination address, which determines the outgoing interface. The frame is then forwarded out the correct port. Error Checking, Automatic Buffering
When the appropriate switch form factor for a network is being determined, what type of switch should be selected when future expansion is important and cost is not a limiting factor?
A modular switch provides fault tolerance and features for bandwidth availability and future expansion by using line cards but is rather costly to implement. Stackable switches provide fault tolerance and bandwidth availability by using special cables between the switches and are less costly to implement than modular switches. A nonstackable switch does not provide these features. A fixed configuration switch is a single switch that does not support features beyond those that originally came with it.
Which impact does adding a Layer 2 switch have on a network?
Adding a Layer 2 switch to a network increases the number of collision domains and increases the size of the broadcast domain. Layer 2 switches do not decrease the amount of broadcast traffic, do not increase the amount of network collisions and do not increase the number of dropped frames.
Which statement is true about broadcast and collision domains?
Adding a switch to a network will increase the size of the broadcast domain. A switch that receives a broadcast frame will forward the frame out all other interfaces, including interfaces that connect to other switches. These switches will also perform the same forwarding action. By adding more switches to the network, the of the broadcast domain increases.
The distribution layer interfaces between the access layer and the core layer to provide many important functions, including:
Aggregating large-scale wiring closet networks Aggregating Layer 2 broadcast domains and Layer 3 routing boundaries Providing intelligent switching, routing, and network access policy functions to access the rest of the network Providing high availability through redundant distribution layer switches to the end-user and equal cost paths to the core Providing differentiated services to various classes of service applications at the edge of the network
Including data services, a converged network with collaboration support may include the following features:
Call control - Telephone call processing, caller ID, call transfer, hold, and conference Voice messaging - Voicemail Mobility - Receive important calls wherever you are Automated attendant - Serve customers faster by routing calls directly to the right department or individual
Stackable Configuration Switches
Connect with a special cable that effectively makes it operate as one large switch.
Common Business Considerations When Selecting Switch Equipment
Cost = number, speed per port, memory, expansion Port Density = enough ports for all the devices Power = powered access points, IP phones, power over ethernet, Reliability = continuous access through a switch Port Speed = speed of the network connection Frame Buffer = memory store on the switch Scalability = ability to grow the system.
What is the destination address in the header of a broadcast frame?
FF-FF-FF-FF-FF-FF The binary format of 11 in hexadecimal is 00010001.
Hierarchy in the Boarderless Switched Network Borderless switched network design guidelines are built upon the following principles:
Hierarchical - Facilitates understanding the role of each device at every tier, simplifies deployment, operation, and management, and reduces fault domains at every tier Modularity - Allows seamless network expansion and integrated service enablement on an on-demand basis Resiliency - Satisfies user expectations for keeping the network always on Flexibility - Allows intelligent traffic load sharing by using all network resources
The following are some important characteristics of switches that contribute to alleviating network congestion:
High port density - Switches have high-port densities: 24- and 48-port switches are often just a single rack unit and operate at speeds of 100 Mb/s, 1 Gb/s, and 10 Gb/s. Large enterprise switches may support many hundreds of ports. Large frame buffers - The ability to store more received frames before having to start dropping them is useful, particularly when there may be congested ports to servers or other parts of the network. Port speed - Depending on the cost of a switch, it may be possible to support a mixture of speeds. Ports of 100 Mb/s, and 1 or 10 Gb/s are common (100 Gb/s is also possible). Fast internal switching - Having fast internal forwarding capabilities allows high performance. The method that is used may be a fast internal bus or shared memory, which affects the overall performance of the switch. Low per-port cost - Switches provide high-port density at a lower cost.
Which service is provided by an automated attendant feature on a converged network?
Increases the speed of voice services by routing calls directly to individuals or departments. Point-to-point video and video conferencing describe video services on a converged network. An IT management interface is part of a converged network solution that allows IT personnel to facilitate moves, adds, and changes through a centralized application.
The fundamental concept of switching refers to a device making a decision based on two criteria:
Ingress port -used to describe where a frame enters the device on a port. egress is used to describe frames leaving the device from a particular port. Destination address
Switches Function to Provide
QoS Vioce and Video Data Security
A switched LAN allows more flexibility, traffic management, and additional features:
Quality of service Additional security Support for wireless networking and connectivity Support for new technologies, such as IP telephony and mobility services
Collapsed Core
A network design where the core and distribution layers are collapsed or combined into a single layer of switches.
Modular Configuration Switches
The chassis accept line cards that contain the ports. The line card fits into the switch chassis the way that expansion cards fit into a PC.
form factor is?
The size and shape of a computer or device.
What are two reasons a network administrator would segment a network with a Layer 2 switch?
to isolate traffic between segments to enhance user bandwidth
Which type of address does a switch use to build the MAC address table?
source MAC address
Which network device can be used to eliminate collisions on an Ethernet network?
A switch provides microsegmentation so that no other device competes for the same Ethernet network bandwidth.