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|style="padding-left:20px;" | Networking Utilities<br>
[http://man7.org/linux/man-pages/man8/ifconfig.8.html ifconfig]<br>
[http://man7.org/linux/man-pages/man8/ip.8.html ip]<br>
[http://www.serverlab.ca/tutorials/linux/administration-linux/configure-centos-6-network-settings/ system-config-network]<br>
[http://man7.org/linux/man-pages/man8/route.8.html route]<br>
[http://man7.org/linux/man-pages/man8/ping.8.html ping]<br>
[http://man7.org/linux/man-pages/man8/arp.8.html arp]<br>
[http://man7.org/linux/man-pages/man8/netstat.8.html netstat]|style="padding-left:20px;" | Networking Configuration Files<br>[httphttps://zenitwww.senecaccentos.onorg/docs/5/html/Deployment_Guide-en-US/s1-networkscripts-interfaces.cahtml Interface Configuration]<br>[https:/wiki/indexlinux.die.phpnet/IPTables iptablesman/5/resolv.conf resolv.conf]<br>
|style="padding-left:20px;" |Additional Utilities<br>
[http://man7.org/linux/man-pages/man1/find.1.html find]<br>
# In the '''Connection Details''' dialog box, select the '''Virtual Networks''' tab
# Click to <u>de-select</u> the '''Autostart (on boot)''' check-box options and click the '''Apply''' button.
# Stop the default network configuration by clicking on the '''stop''' button at the bottom left-side of the dialog box.
# Click the '''add''' button (the button resembles a "plus sign") to add a new network configuration.
# Type the network name called: '''network1''', and then click the '''Forward''' button.
[[Image:new_network_dialog.png|right|thumb|300px|Although the private network has been setup via the '''Virtual Machine Manager''', each virtual machine requires to change its own network setting individually (either '''graphically''' or by '''command line''').]]
=== Part 2: Configuring Network For centos1 VM===
# Configure your '''centos3''' VM (in the '''View''' -> '''Details''' menu of Virtual Machine Manager) to configure the NIC interface to '''network1''', click '''Apply''', and switch your centos3 VM view from ''details'' to '''console'''.
# Start your '''centos3''' VM, login, and su to '''root'''.
# Use the command called: '''ifconfig''' to list active interfaces, you should see one with a name of '''eth0''' or a similar name.<br><br>NOTE: If the '''ifconfig''' command is NOT available in your centos3 vm, issue the command:<br>'''yum install net-tools'''<br><br>
# To configure your card with a static address use the following command:
#:<b><code><span style="color:#3366CC;font-size:1.2em;">ifconfig eth0 192.168.235.13 netmask 255.255.255.0</span></code></b>
# List the contents of this directory. You should see 2 different types of files, network config scripts and network configuration files.
# Look for the configuration file for your original interface, it should be named '''ifcfg-eth0'''
# Edit the new file for you your interface and give it the following settings (or create a brand new file, might be easier than editing the old one):
#::DEVICE=eth0
#::IPADDR=192.168.235.13
'''Answer INVESTIGATION 1 observations / questions in your lab log book.'''
=INVESTIGATION 2: MANAGING YOUR NEWLY-CREATED NETWORK=
Creating private networks are an important task, but a system administrator also needs to manage the network to make it '''convenient to use''', make it '''safer from unauthorized access''', and '''troubleshoot''' network connectivity problems.
This investigation will expose you to useful "tweaks" and utilities to help accomplish this task. '''Lab 7''' requires that you understand these concepts and have a good general understanding how to use these troubleshooting utilities (like '''netstat''' and '''iptables''').
{| width="40%" align="right" cellpadding="10"
|{{Admon/note | Hosts files vs. the Domain Name System | On large public networks like the Internet or even large private networks we use a network service called [http://en.wikipedia.org/wiki/Domain_Name_System Domain Name System (DNS)] to resolve the human friendly hostnames like '''centos.org''' to the numeric addresses used by the IP protocol. On smaller networks we can use the <code>/etc/hosts</code> on each system to resolve names to addresses.}}
|}
=== Part 1: Using /etc/host hosts File for Local Hostname Resolution ===
After setting up a private network, it can be hard to try to remember IP addresses. In this section, we will setup your network to associate easy-to-remember server names with IP ADDRESSES.
=== Part 2: Network Connectivity & Network Service Troubleshooting Utilities===
{| width="40%" align="right" cellpadding="10"
|- valign="top"
|
<table cellspacing="0" cellpadding="5" style="border-top: thin solid black;margin-left:60px;">
<caption>'''Common Network Troubleshooting Tools'''</caption>
<tr valign="top>
<td style="border-bottom: thin solid black;font-weight:bold;background-color:#ffffff;">Purpose</td>
<td style="border-bottom: thin solid black;font-weight:bold;background-color:#ffffff;padding-left:100px;">Command(s)</td>
</tr>
<tr valign="top">
<td style="border-bottom: thin solid black;">Network Connectivity</td>
<td style="border-bottom: thin solid black;padding-left:100px;"><b><code><span style="color:#3366CC;font-size:1.2em;">ping</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">arp</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">ifconfig</span></code></b></td>
</tr>
<tr valign="top">
<td style="border-bottom: thin solid black;">Network Service Status</td>
<td style="border-bottom: thin solid black;padding-left:100px;"><b><code><span style="color:#3366CC;font-size:1.2em;">netstat'''</span></code></b></td>
</tr>
</table>
|}
Troubleshooting network problems is an extremely important and frequent task for a Linux/Unix system administrator. Since network services (such as file-server, print-servers, web-servers, and email-servers) depend on network connectivity, as Linux/Unix sysadmin must be able to quickly and effectively pin-point sources of network problems in order to resolve them.
#Switch to your '''c7host''' machine.
#Issue the '''ping''' command to test connectivity to your '''centos1''', '''centos2''', and '''centos3''' VMs.
#Examine the contents of the ARP cache by using the command: <b><code><span style="color:#3366CC;font-size:1.2em;">arp</span></code></b>arp What is the purpose of ARP?
#Check the contents of the cache again by using the command: <b><code><span style="color:#3366CC;font-size:1.2em;">arp -n</span></code></b> What was the difference in output?
#Issue the following command: <b><code><span style="color:#3366CC;font-size:1.2em;">netstat -at</span></code></b> This command will list all active TCP ports. Note the state of your ports.
#<br>
# Purpose: Creates system info report<br>
#<br># USAGE: ./network-info.bash [full pathname to ifcfg-eno* eth0 file]<br>
<br>
if [ $USER != "root" ] # only runs if logged in as root<br>
if [ $# -ne 1 ]<br>
then<br>
echo "You need to provide the full pathname to ifcfg-eno eth0 file (eg eno1 or eno followed by numbers)" >&2<br> echo "USAGE: $0 [full pathname to ifcfg-eno* eth0 file]" >&2<br>
exit 0<br>
fi
</code>
<br><br>
<ol><li value="7">Give this shell script execute permissions and run this shell script.</li><li>You will need to determine the full pathname of the '''ifcfg-en0ens33''' file in the /etc/sysconfig/network-scripts directory to use as an argument for this shell script.</li><li>Run the shell script. What do you notice from the report that the shell script generated?</li><li>The the Then use wget command to download another variation of the network-info.bash shell script using the awk command to separate the variables and values into separate columns:<br><b><code><span style="color:#3366CC;font-size:1.2em;">httphttps://csict.senecac.onsenecacollege.ca/~murray.saulops235/lab6/network-info-2.bash</span></code></b><br></li></ol>
'''Answer INVESTIGATION 2 observations / questions in your lab log book.'''
= LAB 6 SIGN-OFF (SHOW INSTRUCTOR) =
# Switch to your '''c7host''' VM.
# Change to the '''/root/bin''' directory.
# Issue the Linux command: <b><code><span style="color:#3366CC;font-size:1.2em;">wget httphttps://matrixict.senecac.onsenecacollege.ca/~murray.saulops235/ops235lab6/lab6-check.bash</span></code></b>
# Give the '''lab6-check.bash''' file execute permissions (for the file owner).
# Run the shell script and if any warnings, make fixes and re-run shell script until you receive "congratulations" message.
#Arrange proof of the following on the screen:<br><blockquote><span style="color:green;font-size:1.5em;">✓</span> '''centos2''' VM:<blockquote><ul><li>'''ssh''' from '''centos2''' to '''c7host''' VM.</li></ul></blockquote><span style="color:green;font-size:1.5em;">✓</span>'''c7host''' machine<blockquote><ul><li>A list of your '''iptables''' rules</li><li>Output from running the '''network-info.bash''' shell script</li><li>Run the '''lab6-check.bash''' script in front of your instructor (must have all <b><code><span style="color:#66cc00;border:thin solid black;font-size:1.2em;"> OK </span></code></b> messages)</li></ul></blockquote><span style="color:green;font-size:1.5em;">✓</span> '''Lab6''' log-book filled out.
= Practice For Quizzes, Tests, Midterm & Final Exam =
# What is a port?
# What command will set your IP configuration to 192.168.55.22/255.255.255.0 ?
# What is the difference between UDP and TCP?
# What port number is used for DHCP servers?
# What is the function of the file <code>/etc/hosts</code> ?
# What is the purpose of the file <code>/etc/sysconfig/network-scripts/ifcfg-eth0</code> ?
[[Category:OPS235]]
[[Category:OPS235 Labs]]
[[Category:CentOS 7]]
[[Category:SSD2]]
