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Now you know how to get information about IP address mask hostname of the Linux computer.

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For that you could use multiple commands such as hostname, IP address and ifconfig.

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Now let's use another command like ping traceroute and nslookup and actually we have already used before

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pink command and with pink command you could verify connectivity with remote servers and you could use

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either hostname or IP address of the remote server as argument.

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Let's ping google.com and you'll see actual response from IP address of the google.com server.

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And if I enter ping and use same IP address as was used in this response, let me copy it and paste

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here.

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I'll get actually same response and the reason for that that in networking first we resolve host name

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to IP address and then we connect to specific IP address.

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And that's why here in those responses you see IP address.

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But now question how this Linux computer actually received IP address for Google.com.

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Host name.

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It has actually performed DNS server lookup and you could perform DNS lookup manually using Nslookup

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command.

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And here enter for example again google.com and you'll see answer from the DNS server and DNS server

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for this particular Docker container is here and here is port that is used for DNS lookups.

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It is UDP port and here is actual response from the DNS server.

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And in this block you see actually IP version six IP address for Google.com.

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Here it is.

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And here you see IP version for IP address.

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Here it is.

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It is of course, public IP address because Google.com servers are located in public domain.

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All right.

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Let's now perform one more lookup and let's look up for IP address of the let's say instagram.com.

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And here I see bunch of different IP addresses here is set of IP version six IP addresses and I could

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use actually any of them and above before this section I see again set of different IP addresses that

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were resolved for instagram.com.

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Hostname.

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Here is this long set of different IP addresses and that means that Instagram uses some sort of load

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balancing and we are actually able to connect to any of those IP addresses if we want to reach Instagram.com

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server.

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And if I enter ping instagram.com, I'll get a response from one of the IP addresses from that list.

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Let's stop this output and let's actually search for this IP address.

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Let me copy it.

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Search and actually somewhere above.

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Yes, here it is.

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This address was resolved by DNS server and it is located in this list.

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All right.

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That's how computer actually resolves hostname to IP address.

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And that's how you could perform the same action manually using nslookup command.

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Next command, I want to show you here is trace road trace route and here as argument.

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Let's use google.com hostname.

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And here you see a bunch of IP addresses and actually bunch of different routers that appear on the

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way from this computer to Google.com server.

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And there are actually 11 different routers on this way.

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And for example, here you see private IP address here is also private IP address.

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Here is one more private IP address.

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And here you see some names.

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Next comes one of the public IP addresses.

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Next, one more hostname and so on.

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All those IP addresses starting from this one are actually public IP addresses.

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And that means that here, starting from this step, packets are traveling via public routers with public

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IP addresses.

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All right.

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That's how you could verify connectivity with remote servers using traceroute or pink commands.

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Let's clear the terminal and proceed.

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There is one more command I want to show you here on this lecture.

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And this command is who is with this command.

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You could get information about owner of specific domain.

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For example, let's whois facebook.com.

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Querying.

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And here is information that was retrieved from public registry databases.

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And for example, here you see name servers that are used by Facebook.com, a dot, facebook.com and

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so on.

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You see registrar that was used for registration of this domain.

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You see creation date of this record and it means that this hostname was created in 1997.

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Also on the next line, you see registry expiration date.

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It is set to 2028.

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Alright, let's perform.

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Same query for another host name who is.

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And here let's enter linked in.com.

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Querying.

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And here is the response for linkedin.com domain and information here is similar.

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Here you see set of name servers, domain status information about owner of this domain, information

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about registrar information about creation date and expiration date for this domain.

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Alright, that's all for this lecture where I have demonstrated you how to use such network utility

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commands as ping traceroute and nslookup in order to get IP addresses for a specific host name.

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And you know that in some cases you'll get not just IP version four IP addresses in response, but also

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version six IP addresses.

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And also we have verified connectivity with some of the remote servers.

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Let's now proceed and in the next lecture I'll explain you how to enable SSH on the Linux server and

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afterwards we will connect to Linux server from other computer remotely.

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Let's talk about it next.

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Bye bye.