tailieunhanh - CCNA 1 and 2 Companion Guide, Revised (Cisco Networking Academy Program) part 67

Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 67 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | Page 629 Tuesday May 20 2003 2 53 PM Getting Information About Remote Devices 629 Getting Information About Remote Devices This section describes Telnet ping and traceroute which can be used to obtain information about remote devices as shown in Figure 13-3. Figure 13-3 Testing Process Overview Telnet Telnet is a virtual terminal protocol that is part of the TCP IP protocol suite. Telnet enables you to make connections to remote hosts and makes it possible for a network terminal to remotely log in. telnet is a Cisco IOS Software EXEC command used to verify the application layer software between source and destination. This command is the most complete test mechanism available. Telnet performs at the application layer of the OSI model and it 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 range 0 through 4 specifies five vty or Telnet lines. These five incoming Telnet sessions can take place at one time. Verifying the application layer connectivity is a byproduct of Telnet. Telnet is mainly used to connect to remote network devices such as routers switches and servers to gather information or perform maintenance. It is a simple and universal application program. Establishing and Verifying a Telnet Connection The telnet Cisco IOS Software EXEC command allows a user to Telnet from one Cisco device to another. With the Cisco implementation of TCP IP you do not have to enter the command connect or telnet to establish a Telnet connection. Just enter the host name or the IP address of the remote router. To end a Telnet session use the EXEC commands exit or logout. Figure 13-4 demonstrates initiating and exiting a Telnet connection. B Page 630 Tuesday May 20 2003 2 53 PM 630 Chapter 13 Learning About Neighboring and Remote Devices Figure 13-4 Telnet Operation A host name table or access to DNS for Telnet must be present for a name to work in