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CCNA3 Chapter 1 Notes
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Introduction to Scaling Networks
NOTE: You can use “Ctrl + F” on your keyboard to search for various terms within this document.
These notes may cover:
- Use of hierarchical network.
- Describe recommendations for designing a network
- Describe the types of switches available for small-to-medium-sized business networks.
- Describe types of routers available for small-to-medium-sized business networks.
- Configure and verify basic settings on a Cisco IOS device.
What does scaling a network mean?
- Scaling a network means to expand a network’s organization to accommodate more devices
As networks grow, all enterprise networks must:
- Support critical applications
- Support converged network traffic
- Support diverse business needs
- Provide centralized administrative control.
To provide a highly reliable network, enterprise class equipment is installed in the network.
Hierarchical Design Model
allows access to other networks, such as the internet
see further in the notes for it
allowing access to the users
The primary cisco enterprise architecture modules include:
- Enterprise Campus
- Enterprise Edge
- Service Provider Edge
PSTN and POTS
- What is PSTN?
- ‘PTSN’ stands for Public Switched Telephone Network.
- What is POTS?
- ‘POTS’ stands for Plain Old Telephone System.
- What are they, though?
- They’re telephone systems!
- What are they?
- ‘Failure Domains’ (“FD” or “F”) are areas of a network that are impacted when a specific piece of network equipment experiences problems.
- Other Related Vocabulary
- Switch block deployment
- Each switch block acts independently of the others. Failure of a single device does not impact the whole network.
- Notable Features
- Redundant links are enterprise class equipment and minimize disruption of network.
- Smaller failure domains reduce the impact of a failure on company productivity.
- Smaller failure domains also simplify troubleshooting.
- To create smaller failure domains, you will need to spend more money.
- When creating a network, you must consider them.
Designing for Scalability
- What to Use when Designing a Network for Scalability
- Use expandable, modular equipment or clustered devices.
- Module Usage
- Include design modules that can be added, upgraded, or modified without affecting the design of the other functional areas of the network.
- Addressing Schemes
- Create a hierarchical addressing scheme. (examples: subnetting, vlans, etc)
- NOTE: When using subnets or vlans for a hierarchical network, be careful-- you should consider how many hosts are needed per subnet/vlan.
- For instance, a room with 28 PCs should have the /27 subnet, but for scalability, you should use the /26 subnet.
- Use routers or multilayer switches to limit broadcast and filter traffic.
- Routers will filter the broadcast and reduce traffic in some parts of the network.
Planning for Redundancy
- How do we plan for redundancy?
- For example, you may Install duplicate equipment.
- Provide redundant paths, such as the diagram to the right.
You may use (at least) two examples to increase network bandwidth, such as the following.
- Link Aggregation
- Increases the amount of bandwidth between devices by creating one logical link made up of several physical links.
- A form of link aggregation used in switch networks.
Expanding the Access Layer
- How to be extend/expand the network?
- Access layer connectivity can be extended through wireless connectivity.
Diagram of wireless connectivity expansion to the right.
Fine-Tuning Routing Protocols
- What protocol do you suggest for fine-tuning routing protocols?
- OSPF works well for large, hierarchical networks.
There are four primary form factors:
- Number and Types of ports can be modified
- Multiple switches can be daisy-chained and act as a single unit
- Multiple switches cannot be connected together
- What is port density?
- In a nutshell, it means how many ports are in the device.
- What does forwarding rates mean?
- The processing capabilities of a switch are rated by how much data the switch can process per second.
Power over Ethernet (POE)
- What does power over ethernet mean?
- Power over Ethernet, dubbed “PoE”, permits the carrying of power currents through the data cable (such as a Cat5e cable).
- The primary usage of POE devices are for WAPs and some switches.
- Deployed in the core and distribution layers of an organization's switched network
- Can build a routing table, support a few routing protocols, and forward IP Packets.
What layer are switches placed on?
- Generally, switches are Layer 2; however, multilayer switches can also support layer 3 processes and build routing tables, support routing protocols and forward IP packets.
- Four Roles of Routers
- Broadcast Containment
- Logical Grouping
- VLANs is an example of a logical grouping setup for a router.
The function of the router dictates the configuration of the router.
The four points above (“four roles of routers”) is probably the most common categories for these functions.
- Other Secondary (Additional) Roles of Routers
- Interconnect multiple sites
- Prove redundant paths
- Connect ISPs
- Translate between media types and protocols. Note that switches may do this too.
Three Types of Cisco Routers
- Highly available, 24/7.
- The “lowest common denominator”, if you will.
- Network Edge
- High performance, high security, and reliable service.
- An example of network edge devices could connect a school district (such as CCSD) to a school.
- Service Provider Routers
- These types of devices are usually blade routers.
- Blade routers are related to blade servers, if you need a visualization.
- Fixed Configuration
- Built-in interfaces.
- Slots allow different interfaces to be added.
Managing IOS Files and Licensing
(This is a preview of chapter 9)
Referring to the diagram, this is the pattern Cisco uses for IOS files and licensing.
- Release it
- Maintenance track (‘15M”)
- Keep working (“T T T”)
- Published as working model.
In-Band vs. Out-of-Band Management
- What is In-Band Management?
- In-band management is used to monitor and make configuration changes to a network device over a network connection.
- Configuration of In-Band Requires…
- Requires at least one interface to be connected and operational, and use of Telnet, SSH, or HTTP to access the device.
- What is Out-of-Band Management?
- Out-of-band management is used for initial configuration or when a network connection is unavailable.
- Configuration of Out-of-Band Requires…
- Requires direct connection to console or AUX port and Terminal Emulation client to access device.
Basic Router and Switch Show Commands
The following commands are used to display configurations and verify the existing configurations on routers and switches. They are extremely useful, both in the Packet Tracer realm, and in real life.
Show ip protocols
Displays info about routing protocol configured
Show ip route
Displays routing table info
Show ip ospf neighbor
Displays information about OSPF neighbors
Show ip interfaces
Displays detailed information about interfaces
Show ip interface brief
Displays all interfaces with IP addressing, interface and line protocol status
Show cdp neighbors
Displays information about all directly connected Cisco devices
Displays any port with security enabled.
Show port-security address
Displays all secure MAC addresses.
Displays all MAC addresses the switch has learned.
Hey! If you need to access the Cisco Command Sheet, consider visiting Seeseenayy’s FREE online copy! It contains all of the available commands.
Chapter 1 - Summary
- Introduces the hierarchical network design model that divides the network functionality into the access layer, the distribution layer, and the core layer.
- Describes how the Cisco Enterprise Architecture further divides the network into functional components called modules.
- Defines how routers and multilayer switches are used to limit failure domains.
- Explains that a good networking design includes a scalable IP scheme, fast converging and scalable routing protocols, appropriate Layer 2 protocols and devices that are modular or easily upgraded.
- Identifies that a mission-critical server should have a connection to two different access layer switches. It should also have redundant modules and backup power.
- Recognizes that routers and switches should be selected from the appropriate categories to meet the network's’ requirements.
END OF CHAPTER 1 NOTES
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