Campus LAN Basics – Chapter Summary

The following section is a summary of the major points you should be aware of in this chapter.

Internetwork Design Fundamentals

• Using a structured design methodology provides the following advantages:

1. It ensures that all steps are covered when the process is followed
2. It provides a framework for the design process deliverables
3. It validates that you know how to meet customer and business requirements
4. It allows for consistency in the design and implementation of networks

• Design methodologies are structured approach that include the following steps:

1. Identifying customer requirements
2. Identifying and analyzing the current network
3. Designing network topologies and services
4. Planning the network implementation
5. Proof of concept (building pilots or prototypes)
6. Documenting the network design
7. Implementing and verifying the network design
8. Monitoring and revising the network design

• PPDIOO stands for Prepare, Plan, Design, Implement, Operate, and Optimize
• The Cisco PPDIOO model encompasses all steps from network vision to optimization
• A good, solid implementation plan should include the following items:

1. A checklist of tasks that need to be completed
2. A list of tools and resources needed
3. The schedule of work, coordinated with all needed resources
4. The actual device configurations
5. Documented verification processes and tests
6. A fallback or back-out plan

• In addition to PPDIOO, the following methodologies also include implementation planning

1. Information Technology Infrastructure Library
2. Fault, Configuration, Accounting, Performance, and Security
3. Telecommunications Management Network
4. ISO/IEC 20000
5. Control Objectives for Information and related Technology

SONA and IIN

• The IIN is broken up into three individual phases, which are:

1. Integrated Systems (Integrated Transport)
2. Integrated Services
3. Integrated Applications (AON)

• SONA divides the IIN ideal into three different layers:

1. The Network Infrastructure Layer
2. The Interactive Services Layer
3. The Application Layer

The Hierarchical Design Model

1. In using a hierarchical network design, network changes are easier to make and implement
2. The LAN hierarchical model is comprised of the following three layers:

• The Core Layer
• The Distribution Layer
• The Access Layer

1. The core, or backbone, layer provides optimal transport between sites
2. The distribution layer provides policy-based connectivity
3. The access layer provides workgroup or user access to the LAN

The Enterprise Network Composite Model

• The ECM provides a framework for the design of an enterprise network
• The enterprise network comprises the enterprise campus and the enterprise edge
• The enterprise campus is comprised of the following modules or blocks:

1. The Building or Switch Block or Module
2. The Core Block or Module
3. The Management Block or Module
4. The Server or Server Farm Block or Module
5. The Enterprise Edge Distribution Block or Module

• The enterprise edge is comprised of the following modules or blocks:

1. The Corporate Internet Module or Block
2. The VPN and Remote Access Module or Block
3. The WAN Module or Block
4. The E-Commerce Module or Block

Campus Switched LAN Topologies

• There are three types of topologies that can be used in campus switched LAN design:

1. Scaled Switching
2. Large Switching with Minimal Routing
3. Distributed Routing and Switching

The Different Types of Switching

• Switching can be performed at Layers 1 through 4 of the OSI Model
• The different types of switching are:

1. Physical Layer (Layer 1) Switching
2. Data Link (Layer 2) Switching
3. Network Layer (Layer 3) Switching
4. Transport Layer (Layer 4) Switching
5. Multilayer Switching (MLS)

• Physical Layer switches operate at Layer 1 of the OSI Model
• Physical Layer switches can convert one media type to another
• LAN switches operate at the Data Link layer
• LAN bridges and switches allow you to segment the LAN
• LAN switches have several advantages over bridges:

1. More ports than a bridge would ever be capable of supporting
2. Microsegmentation by allowing individual hosts to be connected to individual ports
3. Operating at hardware speed using ASICs, versus the software used by bridges
4. Supporting Layer 3 and Layer 4 packet switching by including Multi-Layer features
5. Using VLANs to create smaller logical broadcast domains

• The three primary functions of LAN switches are:

1. MAC Address Learning
2. MAC Address Forwarding and Filtering
3. Layer 2 Loop Avoidance and Detection

• Network Layer Switching is similar to the routing of packets at Layer 3
• Layer 3 switching is performed using hardware ASICs
• Layer 3 switching provides the following advantages over Layer 3 routing:

1. Hardware-based packet forwarding
2. High-performance packet switching
3. High-speed scalability
4. Low latency
5. Lower per-port cost
6. Flow accounting
7. Security
8. Quality of service (QoS)

• Layer 4 switching provides additional routing above Layer 3
• Layer 4 switching is also sometimes referred to as Layer 4-7 switching
• Layer 4 switches require a lot of memory
• Multilayer Switching, or MLS, combines Layer 2, Layer 3, and Layer 4 switching
• Cisco supports MLS for both Unicast and Multicast
• In MLS switching, an MLS cache, is maintained for the Layer 3-switched flows
• In Cisco Catalyst switches, MLS requires the following components:

1. Multilayer Switching Engine (MLS-SE)
2. Multilayer Switching Route Processor (MLS-RP)
3. Multilayer Switching Protocol (MLSP)

LAN Switching Fundamentals

• LAN switching is a form of packet switching used in Local Area Networks
• LAN switches provide much higher port density at a lower cost than traditional bridges
• There are three main forwarding techniques that can be used by switches:

1. Store-and-Forward Switching
2. Cut-Through Switching
3. Fragment-Free Switching

• LAN switching can be characterized as either symmetric or asymmetric
• Symmetric switching provides evenly distributed bandwidth to each port on the switch
• Symmetric switching is typically used in a peer-to-peer desktop environment
• Asymmetric switching provides unequal bandwidth between ports on a switch
• Asymmetric switching is the most common type of switching
• Asymmetric switching is optimized for client-server environments

Segmenting the LAN

• The rule of thumb when designing bridged networks was the 80/20 rule
• The Internet and server farms have resulted in modern networks using the 20/80 rule
• The 20/80 rule places a greater burden on the network backbone

Catalyst Switch Table Architectures

• The two table architectures supported by Catalyst switches are:

1. Content Addressable Memory (CAM)
2. Ternary Content Addressable Memory (TCAM)

• CAM uses a key to perform a table lookup
• The key is fed into a hashing algorithm
• The CAM table lookup is based on an exact match
• Ternary CAM (TCAM) offers an enhancement over CAM
• TCAM is based on three values, which are 0, 1, or x
• The TCAM memory structure is divided into a series of patterns and masks
• TCAM has the ability to ignore certain fields
• TCAM uses the longest match rule to match against packets