1. Chapter 1
1.1 LAN Design
1.2 The Switched Environment
Chapter 1

2. Chapter 1: Objectives
Describe the convergence of data, voice, and video in the context of switched networks.
Describe a switched network in a small-to-medium-sized business.
Explain the process of frame forwarding in a switched network.
Compare a collision domain to a broadcast domain.
Chapter 1 Objectives

3. Legacy Telephone Equipment

4. Separate Networks
Voice Network
Video Network
Data Network

5. Converged Networks
Convergence combines voice and video communications on a data network.
The impact of moving a conventional company architecture to a completely converged network creates a shared infrastructure resulting in a single network to manage.
A primary benefit of a converged network is that there is just one physical network to install and manage.
Results in substantial savings over the installation and management of separate voice, video, and data networks.

6. Converged Networks
To support collaboration, business networks employ converged solutions using voice systems, IP phones, voice gateways, video support, and video conferencing.

7. Converged Networks
The convergence of services onto the data network has resulted in an evolution in networks.
It’s gone from a traditional data transport role, to a super-highway for data, voice, and video communication.
Therefore, the converged network must be properly designed and implemented to allow the reliable handling of the various types of information that it must carry.
A structured design is required to allow management of this complex environment.

8. Borderless Networks
The Cisco Borderless Network provides an architectural approach that embeds intelligence, simplifies operations, and is scalable to meet demands of the converged network.
It can connect anyone, anywhere, anytime, on any device - securely, reliably, and seamlessly.
It provides the framework to unify wired and wireless access across many different device types.

9. Network Design Principles
Borderless Networks
Borderless networks are built using following principles:
These are not independent principles, therefore, understanding how each principle fits in the context of the others is critical.
Network Design Principles
Explanation
Hierarchy
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 by keeping the network operational.
Flexibility
Allows intelligent traffic load sharing by using all network resources.

10. Three-tier hierarchical model Two-tier hierarchical model
Borderless Networks
Designing a borderless switched network in a hierarchical fashion allows network designers to overlay security, mobility, and unified communication features.
There are two time-tested and proven hierarchical design frameworks for campus networks.
Three-tier hierarchical model
Two-tier hierarchical model

11. Borderless Networks
Introducing modularity into the campus hierarchical design further ensures that the campus network remains resilient and flexible enough to provide critical network services.
Modularity also helps to allow for growth and changes that occur over time.

12. Role of Switched Networks
Switched networks incorporate the following features:
Layer 3 functionality
Quality of service
IP telephony
Security
Wireless networking
Mobility
Meeting the requirements of next generation networks:
Secure
Reliable and always available
Support converged network traffic such as data, voice, video, security systems, and more
Role of Switched Networks

13. Switch Considerations
There are various types of enterprise switches and the following are features to consider when selecting them.
Consideration
Explanation
Cost
Cost of a switch depends on the number and speed of the interfaces, supported features, and expansion capability.
Port Density
Network switches must support the appropriate number of devices on the network.
Power
Some switches support Power over Ethernet (PoE) .
Some chassis-based switches support redundant power supplies.
Reliability
Switch should provide continuous access to the network.
Port Speed
Speed of the network connection.
Frame Buffers
Switch should be able to store frames for congested ports.
Scalability
Switch should provide the opportunity for growth
Role of Switched Networks

14. Switch Form Factor
Switch form factor refers to the type of switch and the thickness of it when mounted in a rack.
The thickness of the switch is expressed in number of rack units (e.g., 1U, 2U, ….).
Network designers must choose between:
Fixed configuration switch
Modular configuration switch
Stackable or non-stackable switch

15. Fixed Configuration Switches
Fixed configuration switches are basically “what you see is what you get” and they do not support features or options beyond those that originally came with it. 1U

16. Modular Switches
Modular configuration switches are more flexible and typically come with different sized chassis supporting various modular line cards that fit into the switch chassis.

17. Stackable Switches
These switches can be interconnected using a special cable.
They can be daisy-chained and effectively managed as one large switch using the Cisco StackWise technology.

18. L2 and L3 Switches Switches are also identified as either:
Layer 2
Layer 3 (or multilayer switch)
L3 switches are typically deployed in the core and distribution layers of an organization's switched network.
They can build a routing table, support a few routing protocols, and forward IP packets at a rate close to that of Layer 2 forwarding.
Multilayer switches often support specialized hardware, such as application-specific integrated circuits (ASICs).

19. L2 and L3 Switches
There is a trend in networking toward a pure Layer 3 switched environment.
Access layer switches are usually L2 switches.
Most switches now support routing and it is likely that soon all switches will incorporate a route processor because the cost of doing so is decreasing relative to other constraints.
Eventually the term multilayer switch will be redundant.

20. Enterprise Level Switches
Characteristics of enterprise level switches include:
Port Density
High Forwarding Rates
Support for Link Aggregation
Supports higher throughput by combining multiple switch ports

21. Port Density This is the number of ports available on a single switch.
Remember, some of these ports will be used to interconnect the switch to the rest of the network!

22. Forwarding Rate
Defines the processing capabilities of a switch by rating how much data the switch can process per second.
Switch product lines are classified by forwarding rates.
Entry-layer switches have lower forwarding rates than enterprise-layer switches.

23. Forwarding Rate
Wire speed describes the theoretical maximum data transmission rate that each port on the switch is capable of attaining
Because access layer switches are physically limited by their uplinks to the distribution layer they don’t need to operate at full wire speed.
Therefore use:
Less expensive, lower performing switches at the access layer
More expensive, higher performing switches at the distribution and core layers where forwarding rate makes a bigger impact.

24. Link Aggregation
Are there enough ports on a switch to aggregate to support the required bandwidth?
A 24-port switch, with each port capable of running at gigabit speed could generate up to 24 Gb/s of network traffic.
What if this switch is connected to the network with one 1 Gbps link?
Bandwidth contention would occur.
Each port would get 1/24th of the available wire speed.
Data would be forwarded more slowly.

25. Link Aggregation
Link aggregation helps reduce traffic bottlenecks by allowing up to 8 switch ports to be bound together for data communications.
Link aggregation supports higher throughput by combining multiple switch ports.

26. Power over Ethernet (PoE)
Allows the switch to deliver power to a device over the existing Ethernet cabling.
Can provide power to IP phones and wireless access points.

27. PoE Pass-Through Switches
Some switches such as the Cisco Catalyst 2960-C and 3560-C Series compact switches support PoE pass-through.
PoE pass-through allows a network administrator to power PoE devices connected to the switch, as well as the switch itself, by drawing power from certain upstream switches.

28. Enterprise Switches There is no one switch to “switch them all”.
An enterprise would require the services of many different switches based on its function as a core, distribution, and access layer.
Cisco Switches

29. Access Layer Switches Cisco Catalyst 2960 Series
Cisco Catalyst 2960 and 2960-C Series Compact Switches 
Cisco Catalyst Switch Breakdown

30. Catalyst 2960
Entry-layer enterprise, medium-sized, and branch office network switch
Forwarding rates from 16 Gb/s to 32 Gb/s
Multilayered switching
QoS features to support IP communications
Access control lists (ACLs)
Fast Ethernet and Gigabit Ethernet connectivity
Up to 48 10/100 ports or 10/100/1000 ports with additional dual purpose gigabit uplinks
No PoE support
CLI, Web management, Network Assistant, console, AUX access

31. Catalyst 2960

32. Distribution and Access Layer Switches
Cisco Catalyst 3560-X Series 
Cisco Catalyst 3750-X Series
Cisco Catalyst 4500E Series
Cisco Catalyst Switch Breakdown

33. Catalyst 3560
Enterprise-class switch supports PoE, QoS, and advanced security features (ACLs)
Small enterprise LAN access or branch-office converged network environments.
Different fixed configurations:
Fast Ethernet and Gigabit Ethernet connectivity
Up to 48 10/100/1000 ports, plus four small form-factor pluggable (SFP) ports
Optional 10 Gigabit Ethernet connectivity in the Catalyst 3560-E models
Optional Integrated PoE (Cisco pre-standard and IEEE 802.3af); up to 24 ports with 15.4 watts or 48 ports with 7.3 watts

34. Catalyst 3560

35. Catalyst 3750
Access layer switches in midsize organizations and enterprise branch offices
Forwarding rates from 32 Gb/s to 128 Gb/s
Supports Cisco StackWise technology
StackWise technology allows up to 9 switches to be interconnected via the use of a fully redundant backplane.
Different stackable fixed configurations:
Fast Ethernet and Gigabit Ethernet connectivity
Up to 48 10/100/1000 ports, plus four SFP ports
Optional 10 Gigabit Ethernet connectivity in the Catalyst 3750-E models
Optional Integrated PoE (Cisco pre-standard and IEEE 802.3af); up to 24 ports with 15.4 watts or 48 ports with 7.3 watts

36. Catalyst 3750

37. Catalyst 4500
Distribution Layer switch that provides multilayer switching for enterprises, small- to medium-sized businesses, and service providers.
Forwarding rates up to 136 Gb/s
Different modular configurations:
Modular 3, 6, 7, and 10 slot chassis offering different layers of scalability
High port density: up to 384 Fast Ethernet or Gigabit Ethernet ports available in copper or fiber with 10 Gigabit uplinks
PoE (Cisco pre-standard and IEEE 802.3af)
Dual, hot-swappable internal AC or DC power supplies
Advanced hardware-assisted IP routing capabilities

38. Catalyst 4500

39. Core and Distribution Layer Switches
Cisco Catalyst 6500 Series
Cisco Catalyst 4500E Series
Cisco Catalyst 4500-X Series
Cisco Catalyst 3750-X Series
Cisco Catalyst Switch Breakdown

40. Catalyst 6500
Optimized for secure, converged voice, video, and data networks.
Can manage traffic at the distribution and core layers.
Highest performing Cisco switch
Supports forwarding rates up to 720 Gb/s.
Very large network environments found in enterprises, medium-sized businesses, and service providers.

41. Core Layer: Catalyst 6500

42. Catalyst 6500 Different modular configurations:
Modular 3, 4, 6, 9, and 13 slot chassis
LAN/WAN service modules
PoE up to 420 IEEE 802.3af Class 3 (15.4W) PoE devices
Up to /100 ports, /100/1000 ports, 410 SFP Gigabit Ethernet ports, or Gigabit Ethernet ports
Dual, hot-swappable internal AC or DC power supplies
Advanced hardware-assisted IP routing capabilities

43. Switching as a General Concept
The fundamental concept of switching refers to a device making a decision based on two criteria:
Ingress port
Destination address
A LAN switch maintains a MAC Address Table that it uses to determine how to forward traffic through the switch
Switching as a General Concept in Networking and Telecommunications

44. Dynamically Populating a MAC Address Table
As the switch learns the relationship of ports to devices, it builds a table called a MAC address, or content addressable memory (CAM) table.
Dynamically Populating a Switch MAC Address Table

45. Switch Forwarding Methods
Application-specific-integrated circuits (ASICs) reduce the packet-handling time, and allow the device to handle an increased number of ports without degrading performance.
Two Methods of forwarding frames:
Store-and-Forward -  makes a forwarding decision on a frame after it has received the entire frame and checked the frame for errors.
Cut-Through -  begins the forwarding process after the destination MAC address of an incoming frame and the egress port has been determined.
NOTE:
Cisco switches now all use Store and Forward
Switch Forwarding Methods

46. Selective Forwarding Cut-Through Fragment Free Store-and-Forward
Lowest Latency
No error checking
Fragment Free
Low Latency
Checks for collisions
(Filters most errors)
Store-and-Forward
Highest Latency
All errors filtered
Lowest Latency Highest Latency
Less Error Checking More Error Checking

47. Collision Domains Each port on the switch represents a new segment.
Each new segment is a collision domain.
Collision Domains

48. Broadcast Domains
Switches do not filter broadcast frames therefore a collection of interconnected switches forms a single broadcast domain. 
Routers are used to segment both collision and broadcast domains
Broadcast Domains

49. Alleviating Network Congestion
Characteristics of switches that contribute to alleviating network congestion:
Characteristics
Explanation
High port density
Large enterprise switches may support many hundreds of ports.
Large frame buffers
The ability to store many received frames.
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.
Low per-port cost
Switches provide high-port density at a lower cost and can accommodate network designs featuring fewer users per segment, therefore, increasing the average available bandwidth per user.
Alleviating Network Congestion

50. Chapter 1: Summary
The trend in networks is towards convergence using a single set of wires and devices to handle voice, video, and data transmission.
Network resources must now be seamlessly available anytime and anywhere.
The Cisco Borderless Network architecture enables different elements to work together and allow users access to resources from any place at any time.
The traditional three-layer hierarchical design model divides the network into core, distribution, and access layers. It provides modularity, resiliency, and flexibility.
In some networks the functionality of the core layer and the distribution layer are often collapsed together.
It is important to deploy the appropriate types of switches based on network requirements.
Chapter 1 Summary

51. Chapter 1: Summary (cont.)
The network designer must choose between a fixed or modular configuration, and stackable or non-stackable type of switch.
A network administrator may choose to implement a multilayer switch.
Multilayer switches are able to build a routing table, support a few routing protocols, and forward IP packets at a rate close to that of Layer 2 forwarding.
Switches use either store-and-forward or cut-through switching.
Every port on a switch forms a separate collision domain allowing for extremely high-speed full-duplex communication.
Chapter 1 Summary (continued)