CCNA :) Be a Good Network Administrator

Telnet 4.2.1 This page will introduce 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 a Telnet ...

Disabling CDP 4.1.5   This page will show students how to disable CDP. To disable CDP at the global level, use the no cdp run command in global configuration mode. If CDP is disabled globally, individual interfaces cannot be enabled for CDP. On Cisco IOS Release 10.3 or higher, CDP is enabled by default on all supported interfaces to send and receive CDP information. However, on some interfaces, such as asynchronous interfaces, CDP is disabled by default. If CDP is disabled use the cdp enable command in interface configuration mode. To disable CDP on a specific interface after it has been enabled, use the no cdp enable command in interface configuration mode. The next page will introduce some commands that can be used to troubleshoot CDP. Troubleshooting CDP   4.1.6 This page will introduce some commands that can be used to show the version and update CDP information, tables, and traffic: ...

 Creating a network map of the environment 4.1.4 This page will explain how the information that is obtained by CDP can be used to create a network map. CDP was designed and implemented as a simple, low-overhead protocol. Though a CDP frame can be small, it can retrieve a lot of useful information about directly connected Cisco devices. This information can be used to create a network map of the connected devices. To discover devices that are connected to neighbor devices, use Telnet to connect to the neighbors. Then use the show cdp neighbors command. The Lab Activity will show students how to use CDP commands to learn about neighboring network devices. The next page will describe how CDP can be disabled.

Creating a network map of the environment 4.1.4  

Implementation, monitoring, and maintenance of CDP 4.1.3 This page will introduce the commands that are used to implement, monitor, and maintain CDP information:  cdp run cdp enable show cdp traffic clear cdp counters show cdp show cdp entry {*| device-name [*][protocol | version]} show cdp interface [type number] show cdp neighbors [type number] [detail] The cdp run command is used to enable CDP globally on a router. By default, CDP is globally enabled. The cdp enable command is used to enable CDP on a particular interface. On Cisco IOS Release 10.3 or higher, CDP is enabled by default on all supported interfaces to send and receive CDP information. CDP can be enabled on all device interfaces with the cdp enable command. The Lab Activity on this page will teach students about some basic CDP commands. The next page will explain how CDP ca...

Overview Sometimes network documentation is incomplete or inaccurate. Cisco Discovery Protocol (CDP) is a useful tool in these situations because it can build a basic picture of a network. CDP is a media and protocol independent, Cisco proprietary protocol used for neighbor discovery. CDP will only show information about directly connected neighbors but it is still a powerful tool. After a router is initially configured it is often difficult to connect directly to the router for configuration changes or other activities. Telnet is a TCP/IP-based application that allows remote connection to the router command-line interface (CLI) for configuration, monitoring, and troubleshooting purposes. Telnet is an essential tool for network professionals. 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: Ena...

Summary This page summarizes the topics discussed in this module. A router has several modes that are used to accomplish specific tasks. The user EXEC mode is used primarily to check the status of a router. The privileged EXEC mode allows administrators to set usernames and passwords for access to router commands. Global configuration mode is used to apply configuration statements that affect a whole system. One of the first configuration tasks is to give a unique name to a router. For security purposes, passwords and user IDs for authorized users should be set. The show command is used to examine the contents of files and for troubleshooting. Serial interfaces require a clock signal to control the timing of the communications. An interface must have an IP address and subnet mask to route IP packets. By default, interfaces are turned off or disabled. Use the no shutdown command to turn on an interface. Use the show running-config command to display the current running configuration ...

Backing up configuration files 3.2.9  This page will teach students how to backup and restore configuration files using tftp. A current copy of the configuration can be stored on a TFTP server. The copy running-config tftp command can be used to store the current configuration on a network TFTP server, as shown in Figure . To do so, complete the following tasks: Enter the copy running-config tftp command. Enter the IP address of the host where the configuration file will be stored. Enter the name to assign to the configuration file. Answer yes to confirm each choice. A configuration file stored on one of the network servers can be used to configure a router. To do so, complete the following tasks: Use the copy tftp running-config command to enter configuration mode, as shown in Figure . Select ...

Host name resolution 3.2.6   This page will explain how Cisco IOS performs host name resolution. Host name resolution is the process that a computer system uses to associate a host name with an IP address. In order to use host names to communicate with other IP devices, network devices such as routers must be able to associate the host names with IP addresses. A list of host names and their associated IP addresses is called a host table. A host table might include all devices in a network organization. Each unique IP address can have a host name associated with it. The Cisco IOS software maintains a cache of host name-to-address mappings for use by EXEC commands. This cache speeds up the process of converting names to addresses. Host names, unlike DNS names, are significant only on the router on which they are configured. The host table will allow the network administrator to type either the host name such as Auckland or the IP...

Login banners 3.2.4 This page will explain what login banners are and why they are used. A login banner is a message that is displayed at login. Login banners can be used to convey messages that affect all network users, such as scheduled system shutdowns. Login banners can be seen by anyone. Therefore, a banner message should be worded carefully. “Welcome” is an invitation for anyone to enter a router and is probably not an appropriate message. A login banner should warn users not to attempt login unless they are authorized. A message such as “This is a secure system, authorized access only!” informs unwanted visitors that any further intrusion is illegal. The next page will explain how message-of-the-day banners are configured. Configuring message-of-the-day (MOTD) 3.2.5 This page will explain how a message-of-the-day (MOTD) banner can be configured and displayed on all connected terminals.  Enter global configuration ...