51.
What is the purpose of /etc/hostname, if it’s present on the system?
- A.It holds the hostname of a package repository server.
- B.It holds a list of servers that resolve hostnames.
- C.It holds a list of IP addresses and associated hostnames.
- D.It holds the hostname of the local gateway computer.
- E.It holds the computer’s default hostname.
- Answer & Explanation
- Report
Answer : [E]
Explanation :
Explanation :
| Although not all systems use /etc/hostname, option E correctly describes it for those systems that use it. The file or files that hold information on package repository servers vary from one package system to another, so option A is incorrect. Option B describes the purpose of /etc/resolv.conf. Option C describes the purpose of /etc/hosts. Option D doesn’t describe any standard Linux configuration file, although the gateway computer’s IP address is likely to appear in a distribution-specific configuration file. |
52.
Network accesses to parts of the Internet work fine, but several common sites have stopped
responding (even when addressed via raw IP addresses). Which of the following tools will
be most helpful in diagnosing the source of this problem?
- A.netstat
- B.ping
- C.traceroute
- D.ifconfig
- E.dig
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| The traceroute command (option C) identifies the computers that lie between your own computer and a destination computer, along with some very basic information about network packet travel time and reliability. Thus, traceroute can help you track down the source of the described problem—perhaps a router that’s critical to reaching all of the non-responsive systems has failed. The netstat and ifconfig utilities of options A and D both provide information about local network configuration options, but they most likely won’t be of much help in diagnosing a problem that affects only some sites. The ping utility (option B) may help you quickly identify sites that have failed but won’t be of much use beyond that. You can use dig (option E) to obtain information on the mapping of hostnames to IP addresses, but it won’t help in resolving basic connectivity problems. |
53.
The ping utility responds normally when you use it with an IP address but not when you
use it with a hostname that you’re positive corresponds to this IP address. What might
cause this problem? (Select two.)
- A.The target computer may be configured to ignore packets from ping.
- B.Your computer’s DNS configuration may be broken.
- C.The DNS configuration on the target system may be broken.
- D.The route between your computer and its DNS server may be incorrect.
- E.Your computer’s hostname may be set incorrectly in /etc/hostname.
- Answer & Explanation
- Report
Answer : [B, D]
Explanation :
Explanation :
| DNS problems can manifest as an ability to connect to computers using IP addresses but not using hostnames. Thus, options B and D (and various other DNS-related problems) could create the symptoms described. If the target system were configured to ignore ping packets, as described in option A, then it wouldn’t respond when you identified it by IP address. The target system’s DNS configuration (option C) doesn’t enter into the equation, because it responds to the ping request via IP address alone. Your own computer’s locally set hostname (in /etc/hostname) isn’t used by the remote system to reply, so option E is incorrect. |
54.
How can you learn what programs are currently accessing the network on a Linux system?
- A.Type ifconfig -p eth0.
- B.Examine /proc/network/programs.
- C.Type netstat -p.
- D.Examine /etc/xinetd.conf.
- E.Type dmesg | less.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| The netstat program produces various network statistics, including the process IDs (PIDs) and names of programs currently accessing the network when passed the -p parameter. Thus, option C is correct. The ifconfig program can’t produce this information, and the -p option to this program is fictitious, so option A is incorrect. Option B’s /proc/network/programs file is also fictitious. Option C’s /etc/xinetd.conf file is real and may provide some information about some servers that are using the network (as described in Chapter 10); but this file won’t provide information about all servers, much less about clients that are accessing the network. The dmesg command displays the kernel ring buffer, which doesn’t contain information on programs that are currently accessing the network, so option E is incorrect. |
55.
To diagnose a problem with an IMAP server (imap.example.com), you type telnet imap
.example.com 143 from a remote client. How can this procedure help you? (Select two.)
- A.You can verify basic connectivity between the client computer and the server program.
- B.By examining the output, you can locate intermediate routers that are misbehaving.
- C.By using an encrypted protocol, you ensure that problems aren’t caused by a packetsniffing intruder.
- D.Once connected, you can type IMAP commands to test the server’s response to them.
- E.Once you’ve logged into the remote system, you can examine its IMAP log files.
- Answer & Explanation
- Report
Answer : [A, D]
Explanation :
Explanation :
| If you get any response at all, you know that the basic network connection is working, including that the server is responding to the client. With basic knowledge of IMAP commands, telnet enables you to test the server’s responses in more detail than most IMAP clients (mail readers) permit. Thus, options A and D are both correct. Option C describes the functionality of traceroute or tracepath; telnet provides no information about intermediate routers’ functionality, so option B is incorrect. Because neither telnet nor IMAP on port 143 uses encryption, option C is incorrect. Furthermore, a packet sniffer is likely to have no effect on the transfer of data; it just copies the data so that the packet sniffer’s user can see it. Although telnet can be used for remote access in a way that could make option E correct, the question specifies using telnet to connect to port 143, which is the IMAP port, not the Telnet port. Thus, option E is incorrect. (Furthermore, using telnet for remote administration is very risky, since telnet is an unencrypted protocol.) |
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