NAT - SNAT, DNAT, PAT & Port Forwarding

[@IreshDissanayakaM]

Everything at high level in just 9 minutes yet more than enough clarity and slowness to understand. Everything on point. This is awesome! Thank you Sunny.

[@yalidfuentes7985]

He is a great teacher.

[@lauradesouza9980]

He’s a great teacher, I’m learning so much with him!

[@Plainstreamer]

Slow network? To understand it?

[@vadicheg]

wow man i watched 2 other videos had few open questions, watched your 9 minute video and everything is clear now. You are talented teacher

[@na93r]

@Sam Darwin this is a spam

[@asyed1000]

I love how Sunny explains the brief history behind technology in his videos, since at times it is a crucial part in the learning process to understand how the technology came to be and why we need it.

[@biosah]

Simplicity! I love how you slowly and patiently explain complex subjects. Thank you🙏

[@jamesj9744]

Whenever my Udemy instructors are being jive turkeys, I always look up Sunny's Classroom for a clear explanation. This guy is the best!

[@elisdamirchi1447]

I never write comments, but here it goes: Networking topics will be part of my final exam in two weeks and honestly your videos have been such a life saver. I hope you know you're changing lives with your content! Thank you Sir!

[@sunnyclassroom24]

Great to hear!

[@LeirbagIII]

Simple and very well explained. I get back to Sunny anytime I need to review the basics of any topic. Thanks Sunny!

[@lounescharef2441]

Thank you sunny, i have been in the field for over 18 years, no one made the concepts so clear for me, You're the best! I like your chenglish toooooo.

[@PT-ww9nc]

Thank you Sunny, I have been watching many KZbin videos but they do not explained this in such a logical and simple way.

[@bxldragonguy]

Credits to you fir explaining it in such a clear and easy understanding way, thanks!

[@sunnyclassroom24]

You are quite welcome, Steve.

[@haritadepalli959]

Excellent presentation. It is very difficult to find a similar presentation which explained the differences between the 4 concepts as clearly and as easily.

[@syednabeelanwar46]

Thank you sunny , i have gone through all your videos they are well explanatory . you are the Teacher of the century

[@londhe99]

the music at the end is epic ! it gives me recall of life in year 1980s and that time TV shows have this type of music. any way the content is best and crystal clear. good work.

[@sunnyclassroom24]

Thanks a lot for your nice comment! I appreciate your encouragement.

[@AN1MATEK]

Sunny man you always come up when I want to learn something new about networking. Easy, clear but high quality!

[@roberth7830]

Currently learning network services and DNS. So glad to have found your channel. You provide such clear and logical explanations with helpful animations. Thank you for sharing! Subscribed!

[@fatpong6173]

Thank you Sunny, your videos helped me passed a lot of exams

[@Fearless......]

Give this man the nobel peace prize for teaching !

[@zidanetribal2343]

Awesome, Sunny is my to go resource whenever I need to refresh concepts in networking, security and basically IT! Thanks again Sunny for the topnotch content :)

[@devinmorgan4953]

EXCELLENT VIDEO!! This was the explanation that I was missing 🙌🙌🙌

[@sanjayprima]

Excellent . No Other video can be better than to explain NAT-PAT

[@rajivraghu9857]

Thanks Sunny.. you explain stuffs so well. Wish I found these lectures during my engineering..😃

[@sunnyclassroom24]

You are welcome and thank you for your nice comment.

[@AnshumanKumar007]

it's quite interesting how something really helpful and seemingly innoccous has prevented transition to IPV6.

[@virendrabhati6685]

This was a simplest understanding of NAT and type. Examples are very simple and user friendly at each type of NAT describe by Sunny.

[@zhenwang123]

Great video. It is very clear and detailed. Much easier to understand. Thank you Sunny.

[@sunnyclassroom24]

You are welcome!

[@DG-zu4iy]

That moment when you search on youtube and cross your fingers a video with Sunny shows up in the results feed- BINGO! oh Thank Jesus....press PLAY! 😂

[@kooolabo]

Thank you Sunny! clear explanation! To the point! no time wasting.

[@moses5427]

Thank you for the clear and concise explanation as usual. Your videos taught me a lot!

[@simonzhou8416]

Very clear, better than my expensive cissp textbook!

[@sunnyclassroom24]

Thank you for watching!

[@abdullahshaheed4276]

Thank you so much Sunny, I always come back to your lessons. It's my favorite reference.

[@vishalsharmahacks]

Very Nice Explanation. Watched Many. only now all confusions are cleared

[@Mastagon]

I can't say enough good things about Sunny Classroom.

[@sougata7]

Awesome! Each concept clearly explained in a structured way with clearly illustrated charts. What more can one ask for? Great job!

[@sunnyclassroom24]

Great to hear!

[@scienceblossom6197]

I loved this video. Very high quality explanation.

[@sunnyclassroom24]

Thanks a lot or your nice comment.

[@parischarlievij4904]

Thank you Sunny! For putting a number of topics into perspective.

[@lltagged]

Quick, concise and very clear. Thanks!

[@atvid2983]

Thank you sir, the pace and simplicity with which you explain concepts is commendable, when In doubt or want to learn about a subject, I search with Sunny Classroom #####, #### stands for whatever network related concept I am looking for, simple and Brilliant

[@seshansesha7645]

Simple and easy to understand... thank you

[@saidaitbrahim2968]

Wonderful explaining my teacher. Thank you so much

[@FredoCorleone]

Best explantion ever. Sunny is better than Google's IT course in exaplaining NAT, no doubt.

[@dudinhtran3642]

Very useful video, easy to understand and remember. Great job! Many thanks!

[@sunnyclassroom24]

You are welcome!

[@rufusmurphy9990]

A really good explanation, well paced and clear. Thank you

[@JoshuaNartey]

A little confused here Read a book where SNAT means Source Network Address Translation and DNAT means Destination Network Address Translation. The explanation you gave for PAT is what was given for DNAT.

[@prashantbharadwaj3578]

What you read was correct. I am on the same page with you.

[@gustavolautenschlaeger9195]

Wonderful explanation and illustration. Thanks so much!

[@limichael1519]

Hi Sunny Love ur teaching videoes. Thanks for sharing

[@sunnyclassroom24]

you are welcome!

[@quisjourney3688]

thank you very much for the videos, so clear, so easy to understand. Hats off 🤩

[@devinwick5056]

At last I understood. Thank you sunny!

[@armandobarragang]

Sunny, simple and excelent explication. Thanks

[@sunnyclassroom24]

You are welcome!

[@18ShotErnie]

WE LOVE YOU SUNN!!!! THANKS FOR THIS... AND PLENTY OTHER VIDEOS. I REALLY VALUE THE THINGS YOUVE TAUGHT ME

[@gautamr366]

Simply brilliant explanation! Your channel is a boon for anyone looking for good CS fundamentals. Keep it up and hope you can publish topics on Core OS concepts as well?

[@umardelvi5715]

Very clear and concise explanation. Thank you Sir!

[@sunnyclassroom24]

You are welcome!

[@pattygq]

Excellent content as always. Thanks Sunny!

[@dianeventura3270]

IP address conflict @ 3:49 Web Server: 192.168.100.2 and Mail Server: 192.168.100.2

[@sunnyclassroom24]

Thank you very much for pointing that out. I noticed this mistake after I published it. You are very detail-oriented. I appreciate it very much. I will try my best to avoid such mistakes.

[@luthermaria1021]

You deserve more subscribers, this is awesome

[@andygerard228]

Watching our videos always makes my mind feel less stress .

[@mr.b5678]

Best on the web explanation. thanks bud

[@althafahmed5757]

Thats a Beautiful Explanation with some Graphics to explain

[@sunnyclassroom24]

Glad it was helpful!

[@althafahmed5757]

@@sunnyclassroom24 can you explain dmvpn the same way along with configuration? Is there a video tutorial already for dmvpn?

[@michaeleaster1815]

Great video! Thank you... Though I believe 7:25 should be "is 16-bit value", not "16 digit value" ?

[@Helkenberg]

Excellent video. Extremelyt Informative. Subscribed!

[@ashkanizadpanah9761]

Thanks Mr. for your great videos.

[@thepawsupply1501]

Very good Sunny! Thanks for making this video

[@saltech2024]

Awesome!! You are so amazing tutor

[@sunnyclassroom24]

Thanks a lot!

[@mokodo_]

Your videos are amazing, thank you

[@muhammadhakim6038]

one word... AWESOME!!!!!

[@sunnyclassroom24]

Thank you for watching!

[@taddy666]

This is awesome! Thanks for the precision and detail, Sunny.

[@letdo3449]

very great explainations about this 🤗🤗🤗

[@fahadoutlook1241]

you are wonderful teacher.

[@Dertgyhud]

Excellent video!

[@sunnyclassroom24]

Thank you very much!

[@mohishrockstar]

If I understand it uses the TCP port number for uniqueness, now suppose one host using all the available ports (2^16 ports), then how will NATs in the router will map other hosts for incoming traffic?

[@addanametocontinue]

The truth is that your router typically uses more than just port number to track the socket/session. It uses the source IP, sort port, destination IP, destination port. This combination of 4 data points allows it to keep track of a lot more than 65536 sessions.

[@juanpasht]

@@addanametocontinue The combination in raw is: 2^32 src ips * 2^16 src ports * 2^32 dst ips * 2^16 dst ports = 2^96. But normally it is only used 1 unique public IP so it is: 1 src ip * 2^16 src ports * 2^32 dst ips * 2^16 dst ports = 2^64. But also there are some reserved and private IP that are not used as dst ips; they are about 1/8 (en.wikipedia.org/wiki/Reserved_IP_addresses) of the possible 2^32 . About the dst ports, can be used them all (like for port forwarding to one's PC- server), but normally just a few are used, like 25, 80, 443, 5228. So they may not be 2^16, but let's leave them on these 4. We have 1 srcIP * 2^16 srcPorts * (7/8) 2^32 dstIPs * 4 dstPorts = (7/8)2^50 possible combinations-sessions. They are still a lot. If one user is using a public IP address on its PC, then can use all those ~2^50 combinations. For a single outside-server like Facebook (with single public IP let's say), with same port 443 for example, well then yes it is 1 srcIP * 2^16 srcPorts * 1 dstIP * 1 dstport = 2^16 possible combinations-sessions; it is 65536 sessions, that, to be active, need constant activity, because if not, they expire so srcPorts can be reused. All this implies that they are still so that many so that PAT is possible. Let's say it is not a user's PC with public IP but the router with NAT-PAT -the most common form 6:04-; and that 100 devices are connected to it and all browsing Facebok (with 1 public IP address) in same port 443: They share the 65336 combinations the router can give by assigning srcPorts to them all (very improbable all 100 at same time browsing same web but who knows, though it is about 650 srcPorts for each evenly). The router will translate the internal hosts' IPs (with their ports) to all srcPorts as they are available. If, as @Mohan Gyara stated, only 1 device is exhausting the 65536 (surely only with a virus making source DoS) srcPorts, then surely no way the other 99 devices will be able to browse Facebook... but only Facebook, not all the web; without a virus it is almost imposible for 1 device or even 100 devices to exhaust the 65536 srcPorts to one single dstIP and dstPort, and single public srcIP. If the same device or other devices visit KZbin, then it is other IP and other possible combinations of 65536 srcPorts with that different dst IP and Port to be written in the router's NAT table.

[@vinitshandilya]

How amazing this explanation was!! 😀

[@sunnyclassroom24]

Glad it was helpful!

[@naderreda2020]

This is the best video ...... thank you...

[@sunnyclassroom24]

Glad you liked it!

[@ImmiTheKhan]

Awesome explanation Sunny, Subscribed!

[@sairfan06]

great, what i was looking for is, what if we have one public static ip and multiple web servers listing port 80 what we need under our main router to redirect each request?

[@janindubhanuka545]

Great work my friend..

[@sunnyclassroom24]

Thanks for the visit

[@realtebo]

Really good video. If I understand well, what at my home I am doing in my router is only a simple port forwarding. SNAT and DNAT are used at ISP level? Or every home router is using ? and if yes,. .. can yuo explain me how?

[@NicolaeCristian175]

thank you Sunny. Very good video.

[@sunnyclassroom24]

Thank you very much, Nicolae.

Excellent explanation. Thank you.

[@parostpg]

Excellent. Thank you.

[@sunnyclassroom24]

You are welcome!

[@akeelsalman7202]

Another perfect video... Thanks Sunny

[@ferasawwad71]

Greetings to you. Do you need to link the router's internal ip to the router's mac ip address when using Nat feature in order for it to appear to the world? Or link it to the mac ip pc in the restorative section.

[@rkoitsjohncena1258]

Very well explaination, thanks

[@sunnyclassroom24]

You re welcome !

[@premnathkangatharan2193]

Thanks for explaining the differences in the different types of NAT... i was a bit curious how the external unit would know where my request came from, but i think it is by using the PAT by default.

[@derekwang9758]

Very clear video!

[@Man0fMeans]

1:53 Problem! Default Class B mask is two octets, which is /16 and not the /12 shown in the video. Also, Class C mask is three octets, which is /24, not the /16 shown.

[@davidb1132]

Man0fMeans he is showing the subnet mask for private IP addresses. Class B private range only uses the first 12 bits; the first octet, and 4 from the second octet. Class C private range only uses the first 16 bits, or, the first two octet.

[@juanpasht]

​@@davidb1132 I think Man0fMeans is right. Better explained at en.wikipedia.org/wiki/Private_network, the third private range is a Class B or 256 Class C Networks. And the 2nd private network uses 16 Class B, but is not a single Class B.

[@mahikris9625]

how come you are using a Multicast IP@ for mapping to the outside traffic in the section PAT : local IP@ is mapped to : 234.x.x.x:8000 and 234 is in multicast range right ?

[@tomcat2512]

Thank you for this interesting video. It enhances my understanding of NAT. I realized that this video was made quite some time and CGNAT is not yet widely used back then. With the advent of the use of CGNAT by most ISP, it basically deactivates the use of port forwarding in a private network. Do you have a way around this? I would love to see another video on this topic. Thank you!

[@ctsdeveloperx9248]

Great video! Thanks!

[@sunnyclassroom24]

Thanks you for watching!

[@tiruinternationalpublicspe4932]

Awesome Video Sunny , Well Explained !!!

[@StuffOffYouStuff]

Again, the best explained video I've seen on this. Your videos are excellent. I needed a refresh. I do have a couple of clarifying questions about this. 1) Dynamic NAT - what happens if all the public IP addresses are used up? Are internal hosts denied access to the internet then? 2) PAT - If an internal host sends an outgoing packet on port 80, but the gateway then translates that to port 8001, how does the web server on the internet know you are trying to communicate with it on port 80? Thanks, Sunny.

[@juanpasht]

Here is what I think: 1) Yes, they must be denied access until an available public IP comes out; and if not using PAT. 2) The port 80 of the internal host is NATed. The web server doesn't care about that port but the one that comes by 8001 where it will reply the request. The router-gateway receives by 8001 and translates to 80 to the internal host. The web server will never know you tried by the port 80, and doesn't matter.

[@sdputurn]

thanks for video. few questions: 1. can we say PAT is again IP masquerading? 2. i often see people use SNAT as source NAT and DNAT as destination NAT. i am not sure which one is correct. thanks in advance :)

[@arthurimona5901]

Great explanation. Thanks a lot!

[@josecobo7179]

Hi Sunny, thanks for the video. On the PAT explanation, why a common PORT of 80 was chosen instead of a random port number also known as ephemeral port? thank you

[@alexmook6786]

Awesome explanations!!!!!!

[@MRSa-tw6ut]

Very informative, many thanks.

[@123umesho]

Nice explanation. I have a question. Which type is suitable if there are 2 or more web servers and outside people want to access a particular web server. Here only one public ip address is available. Kindly reply please 🙏🙏🙏

[@juanpasht]

One uses port 80 (or 443) and the other you will need another domain that redirects traffic from port 80 (or 443) to the port of the other server. Let's say you have 1.1.1.1 public address. You use as dns: domain1.com so you just use straight port 80 to web server A's port 80 and the same for port 443. And you then use another dns: domain2.com which will redirect from port 80 to the web server por 81, and the same using port 443 to port 444.

[@123umesho]

@@juanpasht sir thank you for the reply. My practical problem is I have two devices which have ip addresses and can be monitored and configured by accessing them through web browser from a computer connected to them through a switch. This is done locally. Now I want to access them remotely. Presently I have one public address. I have configured the modem and put one device ip address in the DMZ settings. By this I am able access only one device remotely. I want to access both the devices remotely. How to do the settings in the modem? I am new to this. Can you help me with this? Thank you!

[@juanpasht]

@@123umesho Hi. Ok is simple. If you just want to access a web server or any service on the other computer (the one is not assigned as DMZ host), just from the modem use port forwarding to the port of this machine. If the 2 devices are 192.168.1.1 and the other 192.168.1.2, and the DMZ is 192.168.1.1, then use port forwarding to 192.168.1.2, let's say you are talking about a web server in port 80 of 192.168.1.2, use a forwarded port from public 80 to private 80, or from public 12345 to private 80. The port forwarding rules are prioritized over the DMZ by the modem, or it should be that way if is not a rare modem hehe. So if 192.168.1.1 is another web server with port 80, and your public IP address is 100.100.100.100, then 100.100.100.100:80 will go to 192.168.1.1:80, and 100.100.100.100:12345 to 192.168.1.2:80. A real problem is when you are using https and port 443, and a FQDN domain name, and an SSL key certified so that the domain is trusted and validated, so you can open my.domain.com to the web server of your choice. Only 1 server. If you want another domain to forward to the 2nd server, it is needed the same port 443 with another FQDN name. So for example I use noip.com for DDNS. You can have many names forwarding to the same public IP. But for 443 to work on both domain names with same public IP... I don't remember if is possible there should be a way (difficult way), but with port 80 and normal http in noip there is an option to forward one domain name to the port 12345 ;D

[@123umesho]

@@juanpasht thank you. I get it.🙂

[@te4683]

Love youre videos. Thx for sharing

[@ekonialancewanariu9049]

Short and sharp. I learnt alot within a short time. A question here please. If I'm using DNAT to connect, should I forget about PNAT? Or can I use them both simultaneously?

[@boblewis1287]

Very good Sunny

[@crystalitsolution9583]

I decided to configure NAT on my ZTE MF29A router but NAT Feature is not present on the Router interface. How do I do it

[@lukevandam7610]

Love you sunny. such helpful vidz

[@sajjadhaider9849]

Awesome Sir.Excellent !

[@sunnyclassroom24]

Thank you !