Thursday, October 1, 2015

Predictable Network Model

Predictable Network Model

Ideally, you should design a network with a predictable behavior in mind to offer low maintenance and high availability. For example, a campus network needs to recover from failures and topology changes quickly and in a predetermined manner. You should scale the network to easily support future expansions and upgrades. With a wide variety of multiprotocol and multicast traffic, the network should be capable of efficiently connecting users with the resources they need, regardless of location.

In other words, design the network around traffic flows rather than a particular type of traffic. Ideally, the network should be arranged so that all end users are located at a
consistent distance from the resources they need to use. If one user at one corner of the network passes through two switches to reach an email server, any other user at any other location in the network should also require two switch hops for email service.

Cisco has refined a hierarchical approach to network design that enables network designers to organize the network into distinct layers of devices. The resulting network is efficient, intelligent, scalable, and easily managed.

Figure 1-4 can be redrawn to emphasize the hierarchy that is emerging. In Figure 1-5 , two layers become apparent: the access layer, where switches are placed closest to the end users; and the distribution layer, where access layer switches are aggregated. 

Figure 1-5 Two-Layer Network Hierarchy Emerges

As the network continues to grow with more buildings, more floors, and larger groups of users, the number of access switches increases. As a result, the number of distribution switches increases. Now things have scaled to the point where the distribution switches need to be aggregated. This is done by adding a third layer to the hierarchy, the core layer , as shown in Figure 1-6 . 

Figure 1-6 Core Layer Emerges

Traffic flows in a campus network can be classified as three types, based on where the network service or resource is located in relation to the end user. Figure 1-7 illustrates the flow types between a PC and some file servers, along with three different paths the traffic might take through the three layers of a network. Table 1-2 also lists the types and the extent of the campus network that is crossed going from any user to the service. 

Figure 1-7 Traffic Flow Paths Through a Network Hierarchy

Table 1-2 Types of Network Services 

Notice how easily the traffic paths can be described. Regardless of where the user is located, the traffic path always begins at the access layer and progresses into the distribution and perhaps into the core layers. Even a path between two users at opposite ends of the network becomes a consistent and predictable access > distribution > core > distribution > access layer.

Each layer has attributes that provide both physical and logical network functions at the appropriate point in the campus network. Understanding each layer and its functions or limitations is important to properly apply the layer in the design process.

Access Layer

The access layer exists where the end users are connected to the network. Access switches usually provide Layer 2 (VLAN) connectivity between users. Devices in this layer,
sometimes called building access switches, should have the following capabilities:
  • Low cost per switch port
  • High port density
  • Scalable uplinks to higher layers
  • High availability
  • Ability to converge network services (that is, data, voice, video)
  • Security features and quality of service (QoS)

Distribution Layer
The distribution layer provides interconnection between the campus network’s access and core layers. Devices in this layer, sometimes called building distribution switches ,
should have the following capabilities:

  • Aggregation of multiple access layer switches
  • High Layer 3 routing throughput for packet handling
  • Security and policy-based connectivity functions
  • QoS features
  • Scalable and redundant high-speed links to the core and access layers

In the distribution layer, uplinks from all access layer devices are aggregated, or come together. The distribution layer switches must be capable of processing the total volume of traffic from all the connected devices. These switches should have a high port density of high-speed links to support the collection of access layer switches.

VLANs and broadcast domains converge at the distribution layer, requiring routing, filtering, and security. The switches at this layer also must be capable of routing packets with high throughput.  Notice that the distribution layer usually is a Layer 3 boundary, where routing meets the VLANs of the access layer.

Core Layer
A campus network’s core layer provides connectivity between all distribution layer devices. The core, sometimes referred to as the backbone, must be capable of switching traffic as efficiently as possible. Core switches should have the following attributes:
  • Very high Layer 3 routing throughput
  • No costly or unnecessary packet manipulations (access lists, packet filtering)
  • Redundancy and resilience for high availability
  • Advanced QoS functions
Devices in a campus network’s core layer or backbone should be optimized for high-performance switching. Because the core layer must handle large amounts of campus-wide data, the core layer should be designed with simplicity and efficiency in mind.

Although campus network design is presented as a three-layer approach (access, distribution, and core layers), the hierarchy can be collapsed or simplified in certain cases. For example, small or medium-size campus networks might not have the size or volume requirements that would require the functions of all three layers. In that case, you could combine the distribution and core layers for simplicity and cost savings. When the distribution and core layers are combined into a single layer of switches, a collapsed core network results.

Enterprise Campus Network Design

Enterprise Campus Network Design

This chapter presents a logical design process that you can use to build a new switched campus network or to modify and improve an existing network. Networks can be designed in layers using a set of building blocks that can organize and streamline even a large, complex campus network. These building blocks can then be placed using several campus design models to provide maximum efficiency, functionality, and scalability.

“Do I Know This Already?” Quiz

The “Do I Know This Already?” quiz allows you to assess whether you should read this entire chapter thoroughly or jump to the “Exam Preparation Tasks” section. If you are in doubt based on your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 1-1 outlines the major headings in this chapter and the “Do I Know This Already?” quiz questions that go with them. You can find the answers in Appendix A , “Answers to the ‘Do I Know This Already?’ Quizzes.”

Hierarchical Network Design

A campus network is an enterprise network consisting of many LANs in one or more buildings, all connected and all usually in the same geographic area. A company typically owns the entire campus network and the physical wiring. Campus networks commonly consist of wired Ethernet LANs and shared wireless LANs.

An understanding of traffic flow is a vital part of the campus network design. You might be able to leverage high-speed LAN technologies and “throw bandwidth” at a network to improve traffic movement. However, the emphasis should be on providing an overall design that is tuned to known, studied, or predicted traffic flows. The network traffic can then be effectively moved and managed, and you can scale the campus network to support future needs.

As a starting point, consider the simple network shown in Figure 1-1 . A collection of PCs, printers, and servers are all connected to the same network segment and use the subnet. All devices on this network segment must share the available bandwidth.

Figure 1-1 Simple Shared Ethernet Network

Recall that if two or more hosts try to transmit at the same time on a shared network,
their frames will collide and interfere. When collisions occur, all hosts must become silent
and wait to retransmit their data. The boundary around such a shared network is called
a collision domain . In Figure 1-1 , the entire shared segment represents one collision

A network segment with six hosts might not seem crowded. Suppose the segment contains hundreds of hosts instead. Now the network might not perform very well if many of the hosts are competing to use the shared media. Through network segmentation, you can reduce the number of stations on a segment. This, in turn, reduces the size of the collision domain and lowers the probability of collisions because fewer stations will try to transmit at a given time.

Broadcast traffic can also present a performance problem on a Layer 2 network because all broadcast frames flood to reach all hosts on a network segment. If the segment is large, the broadcast traffic can grow in proportion and monopolize the available bandwidth. In addition, all hosts on the segment must listen to and process every broadcast frame. To contain broadcast traffic, the idea is to provide a barrier at the edge of a LAN segment so that broadcasts cannot pass or be forwarded outward. The extent of a Layer 2 network, where a broadcast frame can reach, is known as a broadcast domain .

 To limit the size of a collision domain, you can connect smaller numbers of hosts to individual switch interfaces. Ideally, each host should connect to a dedicated switch
interface so that they can operate in full-duplex mode, preventing collisions altogether. Switch interfaces do not propagate collisions, so each interface becomes its own collision domain—even if several interfaces belong to a common VLAN.

 In contrast, when broadcast traffic is forwarded, it is flooded across switch interface boundaries. In fact, broadcast frames will reach every switch interface in a VLAN. In other words, a VLAN defines the extent of a broadcast domain. To reduce the size of a broadcast domain, you can segment a network or break it up into smaller Layer 2 VLANs. The smaller VLANs must be connected by a Layer 3 device, such as a router or a multilayer switch, as shown in Figure 1-2 . The simple network of Figure 1-1 now has two segments or VLANs interconnected by Switch A, a multilayer switch. A Layer 3 device cannot propagate a collision condition from one segment to another, and it will not forward broadcasts between segments.

Figure 1-2 Example of Network Segmentation

The network might continue to grow as more users and devices are added to it. Switch A has a limited number of ports, so it cannot directly connect to every device. Instead, the network segments can be grown by adding a new switch to each, as shown in Figure 1-3 .

Figure 1-3 Expanding a Segmented Network

Switch B aggregates traffic to and from VLAN 1, while Switch C aggregates VLAN 2. As the network continues to grow, more VLANs can be added to support additional applications or user communities. As an example, Figure 1-4 shows how Voice over IP (VoIP) has been implemented by placing IP phones into two new VLANs (10 and 20). The same two aggregating switches can easily support the new VLANs. 

Figure 1-4 Network Growth Through New VLANs

Monday, August 17, 2015

CCNP Routing and Switching SWITCH 300-115 Braindumps

Cisco 300-115 certification exam will definitely lead you to better career prospects. Cisco 300-115 exam can not only validate your skills but also prove your knowledge. Routing and Switching CCNP SWITCH 300-115 dumps is a proven software. With him you will never get better theory. Before you decide to buy, you can try a free trial, so you will know the quality of routing and switching Pass-4Sure CCNP SWITCH 300-115 dumps. It will be your best choice.

Pass-4Sure offers you the chance to download the routing and switching CCNP SWITCH 300-115 dumps. Routing and switching CCNP SWITCH 300-115 dumps follow the same syllabus followed by 300-115 certification exam, we also constantly upgrade our routing and CCNP 300-115 dumps toggle switch so you always get the best and updated information. When you buy the CCNP SWITCH 300-115 routing and switching turns us you get the free updates for all products up to one year, and also you can always extend your update subscription for more period whenever you need it.

For Cisco Certification successfully, you are asked to prepare for it carefully. If you use Pass-4Sure CCNP Routing and Switching SWITCH 300-115 dumps, then you need to do is remember all the questions and answers. As our questions are about the same as truth. We always make sure your pass on your first try, we cannot, unfortunately, give you a full refund. So do not worry about losing your money. If you still doubt our quality, you can go to our website to download some demos to check.

If you use Pass-4Sure CCNP Routing and Switching SWITCH 300-115 dumps, you may experience an actual 300-115 exam. We know exactly what is needed and have all the routing and switching CCNP SWITCH 300-115 dumps that are included in 300-115 training series. Our Routing and Switching CCNP SWITCH 300-115 dumps cover more than 100% of the questions and answers that may appear on your 300-115 exam. Each point of Routing and Switching CCNP SWITCH 300-115 dumps help you take Cisco 300-115 exam much easier and become Cisco certified in not a long time. All materials that offer must can satisfy.

Cisco CCNP 300-115 dumps are cheap and good. We use Cisco CCNP 300-115 dumps dedication to our candidates with ultra-low price and high quality. We sincerely hope you can pass the exam. We offer convenient online service to resolve any Cisco CCNP 300-115 dumps to you.Pass-4Sure is the leader in the final certification exam and test preparation provider Cisco 300-115. Our Cisco CCNP 300-115 dumps are constantly reviewed and updated, with a strong correlation.

The Cisco CCNP 300-115 dumps are written in detail to explain each and every point and completely Cisco CCNP 300-115 dumps that can come in the final exam. In addition Pass-4Sure provides you everything online and you can download anything anytime you want. Cisco CCNP 300-115 dumps are available in Cisco Certification 300-115 pdf format so they can be easily downloaded and used.

Pass-4Sure site has a long history of providing Cisco CCNP 300-115 dumps. It has been a long time in the IT industry certified with the well-known position and visibility. Our Cisco CCNP 300-115 dumps contains questions and answers. Our experienced team of IT experts through their own knowledge and experience to further examine the information examination. It contains the real exam questions, if you want to participate in the certification exam Cisco 300-115, select Pass-4Sure is the unquestionable choice.

With the complete collection of Cisco CCNP 300-115 dumps, has assembled to take you through the preparation of your exam 300-115; you will cover every field and category helping to ready you for your successful Cisco 300-115 test. Before you make your decision to buy 300-115 exam, you can have a try on the free demo. Thus, you can know the quality of practice exam and make your best choice.

300-115 Exam PDF and Test Questions

What is your dream? Don't you want to make a career? The answer must be ok. Then, you need to upgrade and develop yourself. You worked in the IT industry, through what methods can you realize your dream? Taking IT certification exam and getting the certificate are the way to upgrade yourself. At present, Cisco 300-115 exam is very popular. Do you want to get Cisco 300-115 certification? If it is ok, don't hesitate to sign up for the exam. And don't worry about how to pass the test, Pass-4Sure certification training will be with you.

Pass-4Sure have a professional IT team to do research for practice questions and answers of the Cisco 300-115 exam certification exam. They provide a very effective training tools and online services for your. If you want to buy Pass-4Sure products, Pass-4Sure will provide you with the latest, the best quality and very detailed training materials as well as a very accurate exam practice questions and answers to be fully prepared for you to participate in the Cisco certification 300-115 exam. Safely use the questions provided by Pass-4Sure's products. Selecting the Pass-4Sure is equal to be 100% passing the exam.

Pass-4Sure Cisco 300-115 exam study guide can be a lighthouse in your career. Because it contains all 300-115 exam information. Select Pass-4Sure, it can help you to pass the exam. This is absolutely a wise decision. Pass-4Sure is your helper, you can get double the result, only need to pay half the effort.

Are you still worrying about the high difficulty to pass Cisco certification 300-115 exam? Are you still sleeplessly endeavoring to review the book in order to pass Cisco 300-115 exam certification? Do you want to pass Cisco 300-115 exam certification faster? Be quick to select our Pass-4Sure! Having it can quickly fulfill your dreams.

Our 300-115 study guide and training materials of Pass-4Sure are summarized by experienced IT experts, who combine the 300-115 original questions and real answers. Due to our professional team, the passing rate of 300-115 test of our Pass-4Sure is the highest in the 300-115 exam training. So, choosing Pass-4Sure, choosing success.

If you want to choose passing Cisco certification 300-115 exam to make yourself have a more stable position in today's competitive IT area and the professional ability become more powerful, you must have a strong expertise. And passing Cisco certification 300-115 exam is not very simple. Perhaps passing Cisco certification 300-115 exam is a stepping stone to promote yourself in the IT area, but it doesn't need to spend a lot of time and effort to review the relevant knowledge, you can choose to use our Pass-4Sure product, a training tool prepared for the IT certification exams.

300-115 Exam Questions and Answers

Question 1.
What is needed to verify that a newly implemented security solution is performing as expected?

A. a detailed physical and logical topology
B. a cost analysis of the implemented solution
C. detailed logs from the AAA and SNMP servers
D. results from audit testing of the implemented solution

Answer: D

Question 2.
Which method of Layer 3 switching uses a forwarding information base (FIB)?

A. Topology-based switching
B. Demand-based switching
C. Route caching
D. Flow-based switching
E. None of the other alternatives apply

Answer: A

Question 3.
Which two statements are true about best practices in VLAN design? (Choose two.)

A. Routing should occur at the access layer if voice VLANs are utilized. Otherwise, routing should occur at the distribution layer.
B. Routing should always be performed at the distribution layer.
C. VLANs should be localized to a switch.
D. VLANs should be localized to a single switch unless voice VLANs are being utilized.
E. Routing should not be performed between VLANs located on separate switches.

Answer: B,C

Question 4.
If you needed to transport traffic coming from multiple VLANs (connected between switches), and your CTO was insistent on using an open standard, which protocol would you use?

A. 802.11B
B. spanning-tree
C. 802.1Q
F. Q.921

Answer: C

Question 5.
What are some virtues of implementing end-to-end VLANs? (Choose two)

A. End-to-end VLANs are easy to manage.
B. Users are grouped into VLANs independent of a physical location.
C. Each VLAN has a common set of security and resource requirements for all members.
D. Resources are restricted to a single location.

Answer: B,C