CS 176B 

ON  FEBRUARY 22, 2000

(TA: KAMIL SARAC - ksarac@cs)

In this homework you will telnet into a router and use some simple commands to learn various configuration information about it. In addition you will need to consult on-line documentation about the specifications and configuration of the system. The purpose of this assignment is to enable you to learn about one of the fundamental components of networks. The router that you will use is from  CISCO 7200 series routers that has been used for evaluation and experimentation purposes in the NMSL Lab.  (For further information, consult to Cisco web page at www.cisco.com)

You will  need to use the telnet program to access a router and will also need to use the online help system.  In addition you will need to consult on-line documentation at the Cisco web site to get further information.

Accessing to the router

From any GSL/CSIL machine, use telnet to connect to (This is the IP address of the router that you will use). Then,  use cs176bhw3 as a password to log in. The router has more than one command mode. After accessing the router, you will be using a "safe" command mode, meaning that you will not be able to change anything in the  configuration of the router; nor you will be able to bring it down (do not even think about trying to do so).  After completing your homework, you type exit to disconnect from the router.

Help System

As mentioned above, the IOS (the operating system of the router) has an easy-to-use help system. You will need to make extensive use of the help system to answer many of the questions below.

Once you connect to the system, you can display all the available commands by typing a question mark (?) at the prompt.

You can  abbreviate commands and keywords to the number of characters that allow a unique abbreviation. For example, you can abbreviate the lock command to loc. Hovewer, if you enter a nonunique abbreviation, context-sensitive help will provide you with all applicable commands for that abbreviation. For example, entering lo will return lock, login and logout commands.

When using context-sensitive help, the space (or lack of a space) before the question mark (?) is significant. To obtain a list of commands that begin with a particular character sequence, type in those characters followed immediately by the question mark (?). Do not include a space. This form of help is called word help, because it completes a word for you.

To list keywords or arguments, enter a question mark (?) in place of a keyword or argument. Include a space before the question mark. This form of help is called command syntax help, because it remids you which keywords or arguments are applicable based on the command, keyworkds, and arguments you already have entered.


Router# s?
set  show  slip  systat

Router# show ?
 alps           Alps information
  backup         Backup status
  bootflash:     display information about bootflash: file system
  bootvar        Boot and related environment variable
  c7200          Show c7200 information
  calendar       Display the hardware calendar
  cef            Cisco Express Forwarding

Homework Questions

The following questions are prepared for you to learn various characteristics and the current configuration of the router. By using the on-line information at Cisco's site and the help system of the router, answer the questions below. In your answer, please include the command you used to answer the question. If you obtained the info from another source, i.e. a web page, give the URL.

1 -The Cisco IOS user interface is divided into many different modes. The commands available to you at any given time depend on which mode you are currently in. List and briefly describe 5 different command modes.

2 - What "type" of commands are you only allowed to use in the current mode?

3 - What is the version number of the IOS?

4 - How many processes are running on the system. Include an output.

5 - How many (network) IP interfaces are there in the system?

6 - What are the types of each interfaces? What are they used for?

7 - What are the hardware addresses and internet addresses of each interface?

8 - What are the maximum frame lengths that each interface can carry

9 - Which interface seems to be the busiest one? What is the status of the others?

10 -Display the configured protocols.

11 - What routing protocol is used for each interfaces?

12 - How would you see the individual entries in the routing table?

13 - Is there any default route? What is it?

14 - How many different types of network masks are used in table entries?

15 - Is there any common properties among the entries in the routing table? How would you interpret this?

16 - What is the purpose of FLASH memory? What is the content of this memory on the router?

17 - Cisco Discovery Protocol (CDP) provides commands that enables you to access a summary of the multiple protocols and addresses configured on other directly connected routers (look for help under "show cdp"). By using this protocol, figure out directly connected neighbors. Display an output.

18 - Display the status of TCP connections.

Routers support a number of tools (such as ping and trace) to help network management.  Ping is used to test connectivity to a host and trace is used to discover the routes that data packets actually take when traveling to their destination.

19 - Invoke a diagnostic tool for testing connectivity to hosts and www.cs.ucsd.edu. How would you compare the results?

20 - Discover the routes that packets will actually take when traveling to their destinations to www.cs.ucsd.edu. What does the output tell you in terms of the route that packets take place: How many domains do packets travel? How are these domains connected to each other?

21 - What might a process be to break into a router, i.e. a network-based mechanism to learn the important passwords?  How could an administrator maintaining the router protect it from attack?