CCNA :) Be a Good Network Administrator

Router Boot Sequence and Verification 5.1.1   Stages of the router power-on boot sequence This page will describe the router startup sequence. The goal of the startup routines for Cisco IOS software is to start the router operations. A router must reliably connect any configured networks. To do this, the startup routines must do the following: Test the router hardware Find and load the Cisco IOS software Find and apply configuration statements such as protocol functions and interface addresses Figure illustrates the sequence and services that are used to initialize a router. Students can use the Interactive Media Activity to test their familiarity with the router boot sequence. The next page will describe how a Cisco device finds and loads Cisco IOS.

Router Boot Sequence and Verification Overview This page summarizes the topics discussed in this module. A Cisco router cannot operate without the Cisco IOS. Each Cisco router has a predetermined boot-up sequence that is used to locate and load the Cisco IOS. This module will describe the stages and importance of this bootup procedure. Cisco internetworking devices use several different files to operate, such as Cisco IOS images and configuration files. A network administrator must manage these files to ensure that the proper versions are used and that necessary backups are performed. This module also describes the Cisco file system and provides the tools to manage it effectively. This module covers some of the objectives for the CCNA 640-801, INTRO 640-821, and ICND 640-811 exams. - Students who complete this module should be able to perform the following tasks: Identify the stages of the router boot sequence ...

Summary This page summarizes the topics discussed in this module. CDP is used to obtain information about directly connected Cisco devices. This includes the router interfaces the devices are connected to, the interfaces used to make the connections, and the model numbers of the devices. CDP is media and protocol independent, and runs on all Cisco equipment over SNAP. It is a Layer 2 protocol that connects lower physical media and upper network layer protocols. When a Cisco device boots up, CDP starts up automatically and allows the device to detect directly connected Cisco devices that also use CDP. It operates at the data link layer and allows two systems to learn about each other, even if they use different network layer protocols. The show cdp neighbors command is used to display information about the networks that are directly connected to a router. The cdp run command is used to enable CDP globally on a router. The cdp enable command is used to enable CDP on a particular i...

Troubleshooting IP addressing issues 4.2.6  IP address-related problems are the most common problems that occur on IP networks. This page will describe three commands that are used to perform address-related troubleshooting: ping uses the ICMP protocol to verify the hardware connection and the IP address of the network layer. This is a basic test mechanism. telnet verifies the application layer software between a source and a destination. This is the most complete test mechanism available. traceroute locates failures in a path from a source to a destination. This command uses Time to Live values to generate messages from each router along a path. The Lab Activity will require students to configure devices in a WAN and then troubleshoot IP address issues. This page concludes this lesson. The next page will summarize the main points from this module. 

Alternative connectivity tests 4.2.5  This page will introduce some tools that are used to verify basic network connectivity. Many network protocols support an echo protocol. Echo protocols are used to test if protocol packets are routed. The ping command sends a packet to the destination host and then waits for a reply packet from that host. Results from this echo protocol can help evaluate the path-to-host reliability, delays over the path, and whether the host can be reached or is functional. This is a basic test mechanism. This operation can be performed at either the user or privileged EXEC modes. In Figure , the ping target 172.16.1.5 responded to all five datagrams that were sent. Each exclamation point (!) indicates a successful echo. Each period (.) on the display indicates that the application on the router timed out while it waited for a packet echo from a target. The ping user EXEC command can be used to diagnose bas...

Advanced Telnet operation 4.2.4  This page will describe some features that can be used when several Telnet sessions are open at the same time. A user may switch back and forth between these sessions. The number of open sessions that are allowed at one time is defined by the session limit command. Use the commands shown in Figure to escape from one session and resume a previously opened session. A new connection can be made from the EXEC prompt. Multiple Telnet sessions can be used and suspended with the Ctrl-Shift-6 , then x sequence. The session can be resumed with the Enter key. When the Enter key is used, the Cisco IOS will resume the connection to the most recently suspended Telnet connection. If the resume command is used it requires a connection ID. Use the show sessions command to view the connection ID, as shown in Figure . The Lab Activity on this page will show students how to use Telnet to remotely access rout...

Disconnecting and suspending Telnet sessions 4.2.3  This page will introduce two important features of the telnet command. These are the disconnect feature and the suspend feature. A potential problem exists when a Telnet session is suspended and the Enter key is pressed. Cisco IOS software resumes the connection to the most recently suspended Telnet connection. The Enter key is used frequently. With a suspended Telnet session, it is possible to reconnect to another router. This is dangerous when changes are made to the configuration or EXEC commands are used. Always check which router is connected when the suspended Telnet feature is used. The show sessions command will show which Telnet sessions are active. The procedure that is used to disconnect a Telnet session is as follows: Enter the disconnect command. Follow the command with the name or IP address of the router or the session number. An example is as follows: Denver> disconnect paris The proce...

Getting Information about Remote Devices 4.2.1 Telnet Telnet is a virtual terminal protocol that is part of the TCP/IP protocol suite. It allows connections to be made to remote hosts. Telnet provides a network terminal or remote login capability. Telnet is an IOS EXEC command used to verify the application layer software between source and destination. This is the most complete test mechanism available. Telnet functions at the application layer of the OSI model. Telnet depends on TCP to guarantee the correct and orderly delivery of data between the client and server. A router can have simultaneous incoming Telnet sessions. The numbers zero through four are used to specify five vty or Telnet lines. The verification of application layer connectivity is a by-product of Telnet. Telnet is mainly used to establish remote connections to network devices. Telnet is a simple and universal application program. The next page will explain how ...