10.17.1 Answers

10.18 Exercises

1. Use rlogin to another system and run an X application. Set the DISPLAY variable using both hostname and IP address to prevent the unable to open DISPLAY error message. Compare the error message with that caused by xhost error.

2. Experiment with the xhost command to allow and disallow an X-windows application client to connect to the host.

3. Explain the security implication for the .rhost, .netrc, .forward, and hosts.equiv files.

4. Experiment with the content and permission bits of the $HOME/.rhosts file to show the effect on an rsh session from another host.

5. Using a test system that does not affect any user, remove a network adapter.

6. Set the value of the IP forwarding attribute of the network option to something other than 0 (zero) and 1 (one) to show that IP forwarding is enabled if the value of the parameter is set to other than 0 (zero).

7. If possible, test the value of the ipfowarding parameter of the network option to allow pings over multiple subnets on two interface boxes.

8. On a test system that does not affect any user, change the reference to the primary name server by editing the /etc/resolv.conf file. Observe the result when you try to access other hosts by hostname and by IP addresses.

9. On a test system that does not affect any user, change the name resolution default order by editing the /etc/netsvc.conf file, such that /etc/hosts file will be used before the domain name server. Add an entry to the /etc/hosts file, such that the hostname of a system has a different IP address and then try to access that hostname.

10. Set the value of the NSORDER environment value to override the /etc/netsv.conf file.

11. Use the arp command to display, delete, and add entries in the ARP cache

12. On a test system that does not affect any user, change the state of the network interface from active to inactive and observe the results. Remove the network interface and observe the result.

13. Add the network interface back in and make it active again. Perform additional tasks to bring the network back into operation.

14. On a test system that does not affect any user, flush the routing table and try to access hosts on the same and different subnet.

15. On a test system that does not affect any user, change the subnet mask to different values and check if it can still communicate with other hosts.

16. On a test system that does not affect any user, change the thewall value and observe the effect on the buffer pools over a period of time.

17. On a test system that does not affect any user, set the value of various tunable parameters of the network option and observe the result over a period of time.

18. On a test system that does not affect any user, stop the inetd daemon and Telnet to other systems. Ping this test system from another host and try to Telnet to it. Observe the result.

19. On a test system that does not affect any user, change the token ring speed of a token-ring network adapter, or change the connecter type of an Ethernet network adapter and observe the result.

Chapter 11. Printers