Pt.3 Ch.16 Networking

Question 1

What does a ping command send?

Answer 1

a special network packet called an ICMP ECHO_Request to a specified host

Question 2

What is often times done in regard to ping for security reasons?

Answer 2

The network devices are configured to ignore these packets. It partially obscures a host from a potential attacker. It is also common for firewalls to be configured to block ICMP traffic.

Question 3

What would pinging linuxcommand.org on the command line look like?

Answer 3

ping linuxcommand.org

Question 4

How do you interrupt a ping packet?

Answer 4

Ctrl-c

Question 5

What does the traceroute program do?

Answer 5

it lists all the “hops” network traffic takes to get from the local system to a specified host.

Question 6

What information is provided by traceroute?

Answer 6

hostnames, IP addresses, performance data, round-trip time from the local system to the router (x3).

Question 7

How do you get around being withheld information in traceroute?

Answer 7

traceroute -T site.com

traceroute -I site.com

Question 8

What system allows us to examine a system’s network interfaces and routing table?

Answer 8

ip

Question 9

What is the loopback interface?

Answer 9

lo. A virtual interface that the system uses to “talk to itself”. Found via ip a

Question 10

what is eth0

Answer 10

The Ethernet interface

Question 11

When performing casual network diagnostics, what are the important things to look for?

Answer 11

1. the presence of the word UP in the first line for each interface (indicating that the network interface is enabled) 2. the presence of a valid IP address in the inet field on the third line 3. For system usings DHCP, a valid IP address in this field will verify that the DHCP is working.

Question 12

What does DHCP stand for

Answer 12

Dynamic Host Configuration Protocol

Question 13

What is used to examine various network settings and statistics?

Answer 13

netstat

Question 14

How do we examine the network interfaces in our system?

Answer 14

netstat -ie

Question 15

How do we display the kernel’s network routing table?

Answer 15

netstat -r

Question 16

IP addresses that end in zero refer to what?

Answer 16

Networks rather than individual hosts

Question 17

What does FTP stand for?

Answer 17

File Transfer Protocol

Question 18

Why is the original form of ftp not secure?

Answer 18

it sends account names and passwords in cleartext.

Question 19

What file transfer protocol does raspbian have?

Answer 19

sftp

Question 20

What is wget good for?

Answer 20

Downloading content from both web and ftp sites, as well as single files, multiple files, and even entire sites.

Question 21

How would you download the first page of linuxcommand.org?

Answer 21

wget linuxcommand.org

Question 22

What protocol is used for secure communication with Remote Hosts?

Answer 22

Secure Shell (SSH)

Question 23

What two basic problems of secure communication with a remote host does ssh solve?

Answer 23

1. It authenticates that the remote host is who it says it is (thus preventing so-called man-in-the-middle attacks). 2. It encrypts all of the communications between the local and remote hosts.

Question 24

What are the two parts an SSH consists of?

Answer 24

1. an SSH server 2. an SSH client

Question 25

What does an SSH server do and where is it located?

Answer 25

it runs on the remote host and listens for incoming connections (by default on port 22).

Question 26

What does an SSH client do and where does it reside?

Answer 26

It's used on the local system to communicate with the remote server.

Question 27

How does SSH for Ubuntu differ?

Answer 27

It only supplies the SSH client.

Question 28

What do most linux distributions come with for SSH?

Answer 28

OpenSSH from the OpenBSD project

Question 29

What has to happen to enable a system to receive remote connections?

Answer 29

it must have the OpenSSH-server package installed, configured and running, and it must allow incoming network connections on TCP port 22.