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:
- It ensures that all steps are covered when the process is followed
- It provides a framework for the design process deliverables
- It validates that you know how to meet customer and business requirements
- It allows for consistency in the design and implementation of networks
- Design methodologies are structured approach that include the following steps:
- Identifying customer requirements
- Identifying and analyzing the current network
- Designing network topologies and services
- Planning the network implementation
- Proof of concept (building pilots or prototypes)
- Documenting the network design
- Implementing and verifying the network design
- 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:
- A checklist of tasks that need to be completed
- A list of tools and resources needed
- The schedule of work, coordinated with all needed resources
- The actual device configurations
- Documented verification processes and tests
- A fallback or back-out plan
- In addition to PPDIOO, the following methodologies also include implementation planning
- Information Technology Infrastructure Library
- Fault, Configuration, Accounting, Performance, and Security
- Telecommunications Management Network
- ISO/IEC 20000
- Control Objectives for Information and related Technology
SONA and IIN
- The IIN is broken up into three individual phases, which are:
- Integrated Systems (Integrated Transport)
- Integrated Services
- Integrated Applications (AON)
- SONA divides the IIN ideal into three different layers:
- The Network Infrastructure Layer
- The Interactive Services Layer
- The Application Layer
The Hierarchical Design Model
- In using a hierarchical network design, network changes are easier to make and implement
- The LAN hierarchical model is comprised of the following three layers:
- The Core Layer
- The Distribution Layer
- The Access Layer
- The core, or backbone, layer provides optimal transport between sites
- The distribution layer provides policy-based connectivity
- 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:
- The Building or Switch Block or Module
- The Core Block or Module
- The Management Block or Module
- The Server or Server Farm Block or Module
- The Enterprise Edge Distribution Block or Module
- The enterprise edge is comprised of the following modules or blocks:
- The Corporate Internet Module or Block
- The VPN and Remote Access Module or Block
- The WAN Module or Block
- 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:
- Scaled Switching
- Large Switching with Minimal Routing
- 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:
- Physical Layer (Layer 1) Switching
- Data Link (Layer 2) Switching
- Network Layer (Layer 3) Switching
- Transport Layer (Layer 4) Switching
- 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:
- More ports than a bridge would ever be capable of supporting
- Microsegmentation by allowing individual hosts to be connected to individual ports
- Operating at hardware speed using ASICs, versus the software used by bridges
- Supporting Layer 3 and Layer 4 packet switching by including Multi-Layer features
- Using VLANs to create smaller logical broadcast domains
- The three primary functions of LAN switches are:
- MAC Address Learning
- MAC Address Forwarding and Filtering
- 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:
- Hardware-based packet forwarding
- High-performance packet switching
- High-speed scalability
- Low latency
- Lower per-port cost
- Flow accounting
- Security
- 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:
- Multilayer Switching Engine (MLS-SE)
- Multilayer Switching Route Processor (MLS-RP)
- 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:
- Store-and-Forward Switching
- Cut-Through Switching
- 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:
- Content Addressable Memory (CAM)
- 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, orĀ 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