CCNA2 TEL III CHAPTER 1

CCNA2 TEL III CHAPTER 1

1. Chapter 1: Routing Concepts

   • Networks allow people to communicate, collaborate and interact in many ways. The networks are used to access web pages, talk via IP phones, participate in videoconferences, compete in interactive games, make purchases on the Internet, complete online course work, and more.
     • • Characteristics of a network
         • Routers are computers
           • Routers interconnect networks
           • Routers choose the best routes
             • The main functions of a router are the following: Determine the best route to send packages. Forward packets to your destination
               • Routers use static routes and dynamic routing protocols to discover remote networks and create their routing tables.

2. Package Forwarding Mechanisms

3. Connection to a network

   • Typically, network devices and end users connect to a network using a wired Ethernet connection or a wireless connection. The LANs shown in the illustration serve as an example of how users and network devices can connect to networks.
   • Default gateways
     • Usually, the default gateway is the address of the interface on the router that connects to the local network. The router maintains routing table entries for all connected networks, as well as remote network inputs, and determines the best route to reach those destinations.

4. Network Address Registration

   • When a new network is designed or assignments are made in an existing network, it is necessary to document the network. At a minimum, the registry must identify the following: Device Names Interfaces used in the design IP addresses and subnet masks Default Gateway Addresses

5. Enabling IP on a host

6. Device LED

   • Host computers connect to a wired network using a network interface and an RJ-45 Ethernet cable. Most network interfaces have one or two LED link indicators next to the interface. Generally, a green LED indicates a correct connection, while a flashing green LED indicates network activity. The function of LEDs varies among computer manufacturers.

7. Console access

8. Enabling IP on a switch

   • Network infrastructure devices require IP addresses to enable remote administration. With the device's IP address, the network administrator can connect to the device remotely using Telnet, SSH, HTTP or HTTPS.

9. Configuration of basic router parameters

   • Cisco routers and switches have many similarities. They support modal operating systems and similar command structures, as well as many of the same commands. In addition, the initial configuration steps are similar for both devices.

10. Command History Feature

    • The command history feature is useful, as it temporarily stores the list of executed commands that must be retrieved. To retrieve commands from the history buffer, press Ctrl + P or the Up arrow key. The result of the commands begins with the most recent command. Repeat the key sequence to successively retrieve the oldest commands. To return to the most recent commands in the history buffer, press Ctrl + N or the Down Arrow key. Repeat the key sequence to successively retrieve the most recent commands.

11. IPv4 router interface configuration

12. IPv6 router interface configuration

    • The configuration of an IPv6 interface is similar to the configuration of an interface for IPv4. Most of the Cisco IOS IPv6 configuration and verification commands are very similar to their IPv4 equivalents. In most cases, the only difference is the use of ipv6 instead of ip in the commands.

13. IPv4 loopback interface configuration

    • The loopback interface is an internal logical interface of the router. This is not assigned to a physical port and, therefore, can never be connected to another device. It is considered a software interface that is automatically placed in the "up" state (active), provided the router is running. The loopback interface is useful for testing and managing a Cisco IOS device, as it ensures that at least one interface is always available. For example, it can be used for testing purposes, such as testing internal routing processes, by emulating networks behind the router.

14. Interface Configuration Verification

    • There are several show commands that can be used to verify the operation and configuration of an interface. The following three commands are particularly useful for quickly identifying the status of an interface: show ip interface brief: shows a summary of all interfaces, including the IPv4 address of the interface and the current operating status. show ip route: shows the contents of the IPv4 routing table that is stored in RAM. In Cisco IOS 15, active interfaces must appear in the routing table with two related entries identified with the code "C" (connected) or "L" (local). In previous versions of IOS, only a single entry with the code "C" appears. show running-config interface interface-id: shows the commands configured on the specified interface.

15. IPv6 interface configuration verification

    • The commands to verify the IPv6 interface configuration are similar to the commands used for IPv4. The show ipv6 interface brief command in Figure 1 shows a summary for each of the interfaces. The result "up / up" on the same line as the interface name indicates the layer 1 / layer 2 interface status. This is the same as the Status and Protocol columns in the equivalent IPv4 command.

16. Router switching function

    • One of the main functions of a router is to forward packets to its destination. This is achieved through a switching function, which is the process that a router uses to accept a packet in one interface and forward it through another interface. A key responsibility of the switching function is to encapsulate the packets in the correct data link frame type for the output data link.

17. Sending a package

18. Forward to the next hop

19. Get to the destination

20. Routing decisions

21. The best way

    • The determination of the best route implies the evaluation of several routes to the same destination network and the selection of the optimal or shortest route to reach that network. When there are several routes to the same network, each route uses a different output interface on the router to reach that network.

22. Load balance

23. Administrative distance

    • It is possible to configure a router with several routing protocols and several static routes. If this occurs, the routing table can have more than one route source for the same destination network. For example, if RIP and EIGRP are configured on a router, both routing protocols can discover the same destination network. However, each routing protocol may decide to take a different route to reach the destination according to the metrics of that routing protocol. RIP chooses a route according to the hop count, while EIGRP chooses a route according to the composite metric. How does the router know which route to use?

24. Routing table

25. A router's routing table stores information about the following: Directly connected routes: these routes come from the router's active interfaces. Routers add a directly connected route when an interface is configured with an IP address and activated. Remote routes: these are remote networks connected to other routers. The routes that go to these networks can be configured statically or learn dynamically using dynamic routing protocols.

    • Origins of the routing table

26. Remote network routing table entries

27. Static routes

28. Dynamic routing

29. IPv4 routing protocols

    • A router that executes a dynamic routing protocol not only determines the best route to a network, but also determines a new better route if the initial route becomes unusable (or if the topology changes). For these reasons, dynamic routing protocols represent an advantage over static routes. Routers that use dynamic routing protocols automatically share routing information with other routers and compensate for any topology changes without the involvement of the network administrator.

30. IPv6 routing protocols

    • As shown in the figure, ISR devices support IPv6 dynamic routing protocols, including the following: RIPng (RIP of last generation) OSPFv3 EIGRP for IPv6

31. Routing concepts

    • There are many key features related to the structures and performance to which we refer when we talk about networks: topology, speed, cost, security, availability, scalability and reliability. Cisco routers and switches have many similarities. They support modal operating systems and similar command structures, as well as many of the same commands. A feature that distinguishes switches from routers is the type of interfaces each supports. Once an interface is configured on both devices, the appropriate show commands must be used to verify that the interface works. The main objective of a router is to connect multiple networks and forward packets from one network to the next. This means that a router usually has multiple interfaces. Each interface is a member or host on a different IP network.

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