DNS Resolution, Step by Step

[@NetworkSP1901]

I don't think I've ever seen such a simple way of explaining this, thank you!!

[@jundossantos]

This video is 9 years old but still paying dividends. Thank you so much for making this topic so easy to understand!

[@AlexAlex-869]

Thanks mate, despite this video being 11 years old it still helps out people like me years later.

[@ZerOv07]

This series was very well explained and straight to the point. I wish that you publish more videos about DNS and networking. Thanks a lot for this quality content.

[@Elyash-pv4in]

thank you sir , it's an awesome view of dns work . who came back in 2024 !

[@brodierobson4490]

Watched all your vids for DNS, as Im studying networking.. brilliant work

[@muralis4508]

great explanation.. very easily explained. why did you stop making further videos on DNS?

[@pinch-of-salt]

Best explanation out there for DNS resolution.

[@boluwatifeogundeyi9206]

This right here just cleared up my doubts on DNS, Thank you 😊

[@rsb4255]

Absolutely brilliant explanation on DNS - you are a master lecturer. Thank you.

[@vladislavkaras491]

Really great videos! It was a great playlist of yours! Thank you very much!

[@profbbrown]

Glad you liked it!

[@Kennerdoll]

As simple as that... Excellent bro

[@helloworldfromvn]

Thank you for such a detailed explanation of DNS resolution process and DNS zones! But, please make more videos on DNS resource record types and DNS zone files, I am really looking forward to these topics from you!!

[@redonakajmaku]

You say that you are going to cover up the reverse lookup in another video. I am not able to find it. Is it uploaded? I would really appreciate it. Your videos are really helpful and make it so easy to grasp the concepts. Thank you!

[@profbbrown]

Alas, I have not yet made that video. :(

[@olijones9953]

@@profbbrown Please continue this series on DNS or something else on Computer Networks, you breakdown all of the information superbly

[@joshpadnick7069]

Great video, Barry. I love the simple approach. Very easy to understand.

[@sahilrally4491]

Great series, thanks , unfortunately everyone stops at this exact spot. I am looking for further like following 1. Linux commands to see . Probably any visual tool. 2. How to configure DNS server on local computer.

[@yaeljad6012]

I guess im asking the wrong place but does anyone know a trick to get back into an instagram account..? I was dumb lost the account password. I appreciate any tricks you can offer me

[@miguelchris6374]

@Yael Jad instablaster =)

[@yaeljad6012]

@Miguel Chris Thanks for your reply. I got to the site through google and I'm trying it out now. I see it takes quite some time so I will get back to you later when my account password hopefully is recovered.

[@yaeljad6012]

@Miguel Chris it did the trick and I actually got access to my account again. I'm so happy! Thanks so much you really help me out !

[@miguelchris6374]

@Yael Jad glad I could help :D

[@baksons]

Thanks a lot mate. So simple every body can clear there concepts with these videos.

[@DMDPS]

Hi, I found this explanation awesome. I understood the RECURSIVE QUERY but could you please explain the AUTHORITATIVE and NON-AUTHORITATIVE ANSWER in this example? Thanks you!

[@gkcoolway]

so basically the step where the ip adress from yahoo.com was cached and the client asks the isp if there is such a ip adress cached and it gets a response with yes is the iterative method?

[@mr.oxfordcomma352]

It is also important to note that the .com name server here is just one out many servers that serve the same zone redundantly.

[@crazytravellerzzz2002]

a very nice explanation sir

[@trestenpool9045]

Awesome little series!!! Thank you very much

[@HyperionCR]

Barry - these concepts are very well explained, very much like khan academy. Similar style too. Hope to see more!

[@profbbrown]

I'd be lying if I said I wasn't influenced by Khan at the time. But I've since gone off in a slightly different -- and hopefully better -- direction.

[@subhasreemukherjee9068]

very nice explanation Sir!

[@asds92]

I've been in IT for over 20 years. I assumed I knew how DNS actually worked until this video. It's so clear that I almost feel STUPID! Thanks for this

[@itsfarseen]

Hi, could you explain the different types of DNS queries - NS, A, etc?

[@profbbrown]

An "A" query is for the IP address of a hostname. An NS query is for the name servers of a domain. An AAAA query is for the IPv6 address of a hostname.

[@andrebode3635]

Hi Barry, very cool presentaion. Could you explain how the CVE-2014-8500 affects the DNS recusive lookup?

[@Aquahutch702]

So question: if another client sends a query for another .com domain (www.youtube.com for example) and the ISP recursive server at 10.5.1.8 does not have the resolved IP address cached, does it at least cache the root zone's response to reach the .com nameserver at c.gtld-servers.net at 198.41.0.4, and thus, forward the query straight to .com zone instead of asking again from the root zone?

[@RajivKumar-ee7xv]

had seen this video and forgot the mechanism. Back here after same question was asked in an interview and I didn't answer. Poor me :-(

[@NewToneMusicOfficial]

😂Did you get the job?

[@RajivKumar-ee7xv]

@@NewToneMusicOfficial I had answered all other questions except this and one more on wws. and cleared that 1st round. Hope you will still be in same euphoria :-p

[@djpunisha29]

flawless explanation , thank you Barry

[@novito]

Really good explanation

[@Trinaldi01]

Excellent video! Nice job.

[@NAB420]

Excellent job...Can I know which software you are using for drawing that flow please?

[@bilbobaggins8605]

So the Icp keeps trading with the other boxes information until it builds up and comes back to it?

[@CFH298]

Amazing video! More videos please!

[@nishantgola139]

Thank you for the easy explanation.

[@nathanielokogie2268]

Thanks Barry, great presentation

[@RamGopalKS]

Thanks for posting such a good video.

[@nverkhachoyan]

I want more videos! Thank you.

[@scotthanley5474]

Superb tutorial, many thanks for uploading. Looking forward to future videos (Y)

[@voipims]

why does root server directly return with response to contact yahoo.com server than .com server ?

So easy to understand! Thank you!

[@dinkydigital8228]

Excellent video

[@samim___3548]

good explanation. thanks

[@AmitKumar-qu9se]

Yahoo.com must be running on some port, right? How does the host computer know which port the application is running on?

[@profbbrown]

All DNS servers operate on port 53, usually using UDP rather than TCP.

[@-DevBhadiyadra]

great video on great topic

[@profbbrown]

Glad you think so!

[@sevaravindranadh2767]

Show the resolution of domain to ip address and ip address to domain pls explain this🙏

[@rajeshwari.p2738]

how do the zone file in ISP looks like ... Whether there will be A record / NS record ??? just please explain the same.. Ex : how the ISP find the root IP address ?

[@i3igmind]

Simply Amazing explanation. I love the way you presented this material. how simple and straight to the point. Good job man! please do more vids. Quick question, which application are you using for your white boarding ? Thanks

[@apall2764]

I was desperate for a simple DNS Resolution answer like that!

[@essjay1568]

Thanks for this brilliant video on DNS Resolution. It helped me clear my doubts significantly. But I still have one doubt ie what if, considering this example only, yahoo changes its server IP address. Will local ISP resolve it still from cached data, and if not how will it get to know that IP is changed for Yahoo. Appreciate your thoughts on it.

[@m0nk051]

Awesome video, thanks a lot. Thats simple and to the point... Waiting for more videos !!! thanks again

[@ejimenez0001]

Thanks Barry. Great video explanation! I appreciate it.

[@josecobo7179]

Best explanation Ever!

[@brx360x]

Is the cache where the ISP stores the resolved IP address to www.yahoo.com the ARP cache for that ISP's DNS sever?

[@profbbrown]

The ARP cache is separate from the DNS cache. Your ISP stores the IP addresses for hostnames in its DNS cache. The ARP cache stores MAC addresses and IP addresses.

[@Ken-kj9ze]

Very well explained.

[@mr.oxfordcomma352]

I really loved this DNS explanation videos! How does the non-recursive case work? The DNS resolver at the client does the whole process himself?

[@profbbrown]

That's correct. The server will just respond with NS entries and the resolver needs to do all the work.

[@bazocallaghan]

Outstanding, thanks Barry.

[@mimahmed95]

Great Explain

[@hafizjoundysyafie8184]

wow, superb explanation, thank you very much :D

[@paulobazuka8165]

Great content. Thank you for sharing it.

[@bennelson6518]

Thank you for teaching so well!

[@MinasyanVahe]

Thank you for the great video. I finally understood how it works!!!

[@silviawessels2462]

What is the cool blackboard app you are using? Great black boarding on all of these videos! Very helpful. Thank you!

[@profbbrown]

Thanks! It's Sketchbook Express on a Wacom Cintiq tablet.

[@definitelynotadam]

Barry Brown simple and precise explanation. It would be nice if you could create another video about reverse lookup DNS :)

[@profbbrown]

***** Thank you. I plan to make more videos and finish the series. Watch for them soon!

[@definitelynotadam]

In that case I suggest exploring DNS tunnelling threat too. I noticed many people get it wrong :)

[@Corvin666]

+Barry Brown, these are awesome videos, thank you so much for putting them together! Have you had the chance to create further videos?

[@masteromelion]

Just OMG, couldn't be explained easier. WELL DONE, like + sub!

[@RottenbergZhenya]

Thank you! Well explained

[@profbbrown]

Glad it was helpful!

[@HudaAlAdheedi]

You are so perfect. It is amazing video I got all the basic info in more details. Thanx :)

[@jj-pg2dk]

What is Yahoo

[@profbbrown]

At least I didn't use MySpace...

[@eliaszeray7981]

simple and detail. Thank u.

[@Abdullahs321]

why cant isp directly asks yahoo server?

[@profbbrown]

The ISP doesn't know the address of Yahoo's name server, so it can't query it directly. It learns the address by going down the chain of servers starting at the root server. In reality, an ISP would cache the information about Yahoo's servers so it can go to them directly for future queries.

[@superthommy]

Isn't this an iterated query? The different DNS-servers sends the response ( i dont know, ask this server ) back to the ISP, instead of asking the lower level DNS-server directly.

[@Bakepichai]

neatly explained

[@jondiyolahe]

Thanks a lot , you filled the gab i have n mind.

[@antolintxit]

Super!!! And reverse lookuup video?? :) Thanks so much!!

[@agnesensen4900]

oh those videos are such a big help! really & trully amasing expalantion, thank you sooooo much! :)

[@saikirangoud9862]

well explained

[@subhajitmitra8937]

Video was very much helpful :)

[@evertonsantosdeandradejuni3787]

Joe Rogan teaching me, i luv it

[@julianwildauer]

great explanation thx!

[@wejoetadory1632]

Thanks

[@muhammadsuleman8771]

Bravo!

[@qanaasalih5030]

thank u so much i appreciate your help

[@thecodingjournal4726]

Thank you barry

[@mbalasubramanian9658]

This is an iterative query example, not a recursive query!

[@thearcticfox13]

Wonderful! Thanks!

[@wirahha]

Great videos thx !

[@acko0326]

thank you man!

[@joshsommer636]

Amazing, thanks a lot!!

[@tranceprince9217]

thank you great video!

[@MaheshYadav-um3go]

thanks, was really helpful

[@elegantic3832]

Its not a virus? Right?

[@anupammaurya6624]

Amazing

[@punefk123]

Perfect....... thanks a lot

[@shnaibdaib98]

Much appreciated

[@romesan2011]

EXCELLENT!!!

[@Selma-rf5mt]

thanks!

[@manikantapalo4426]

thnkz a lott barry!!!

[@darrenng4531]

Hi Barry, the example you have given is NOT a recursive query. A recursive query puts burden of name resolution on the contacted name server, with heavy load at the upper levels of hierarchy. eg. HOST -> LOCAL DNS -> ROOT -> TLD -> AUTH DNS -> IP (reverse). The example you have given is iterative where the (ROOT, TLD, AUTH) replies with names of server to contact.

[@profbbrown]

You're right. In a future version of this video I will try to use more correct terminology. However, the example I've shown in a mixture of recursive and iterative. The initial query from the client to ISP is recursive; the remainder of them (from ISP through the hierarchy) is iterative. I wanted to show here how an external DNS server can do most of the work for the client via a recursive call, rather than the client doing all the work itself.

[@Nekrozys]

Isn't it more like: Recursive: Do you know the IP of www.yahoo.com ? Root: No but .com might know. (NS) Recursive: Ok, then do you know the IP of .com ? Root: Yes, it's X.X.X.X (A) instead of: Recursive: Do you know the IP of www.yahoo.com ? Root: No but .com might know AND its IP is X.X.X.X (NS + A in one request ?) ?

[@RaleignEli-h7l]

Walker Patricia Jackson Steven Thompson Gary