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'''Perform the following steps:'''
# Perform this section on Switch to your c7host machine.#Issue the '''c7hostping'''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. TCP is a connection oriented protocol that uses a handshaking mechanism to establish a connection. Those ports that show a state of LISTEN are waiting for connection requests to a particular service. For example you should see the ssh service in a LISTEN state as it is waiting for connections. <ol><li value="6">From one of your VM' machines login to your host using ssh.</li><li>On your c7host VM rerun the <b><code><span style="color:#3366CC;font-size:1.2em;">netstat -at</span></code></b> command and in addition to the LISTEN port it should list a 2nd entry with a state of ESTABLISHED. This shows that there is a current connection to your ssh server.</li><li>Exit your ssh connection from the VM and rerun the command on the CentOS host. Instead of ESTABLISHED it should now show a state of CLOSE_WAIT. Indicating that the TCP connection is being closed.</li><li>On your c7host VM, try the command: <b><code><span style="color:# x3366CC;font-size:1.2em;">netstat -atn</span></code></b> How is this output different?Without the -n option netstat attempts to resolve IP addresses to host names (using /etc/hosts) and port numbers to service names (using /etc/services)</li><li>Examine the /etc/services file and find which ports are used for the services: ssh, sftp, http</li><li>Now execute the command netstat -au What is the difference between the options: -at and -au? When examining UDP ports why is there no state?</li></ol>
