OSPF Hello Packets :: Area Types (Stub/NSSA) :: BDR/DR :: Practical OSPF
Вставка
- Опубліковано 3 сер 2024
- In this lesson we take a look at Hello Packets and explore all the items they contain. Understanding the content of a Hello packet will show us the requirements for OSPF Routers to become Neighbors with each other.
The Hello packet also includes Area Type and BDR/DR/Priority, which allows us to explain the ideas of Stub areas and Not So Stubby Areas (NSSA). As well as the concepts of the Designated Router (DR), Backup Designated Router (BDR), and the Priority Number.
Here are all the contents of a Hello packet that are explained: Router ID, Area ID, Authentication Data, Network Mask, Hello Interval, Dead Interval, Area Type, Priority Number, Designated Router, Backup Designated Router, and Active Neighbors fields.
This is Lesson 3 of the Practical OSPF series:
• Practical OSPF
00:00 - Start
00:12 - Hello Packet Introduction
01:43 - Router ID
02:36 - Hello Interval / Dead Interval
03:39 - Neighbors Field
05:03 - Area ID
05:18 - Authentication Data
05:51 - Network Mask
06:03 - Area Type / DR / BDR Introduction
06:19 - Normal Area, Stub Area, Not So Stubby Area (NSSA)
11:20 - Designated Router, Backup Designated Router, Priority
14:13 - When does DR/BDR election take place? Multi Access Links
15:35 - What fields must Match in Hello Packets?
17:47 - Outro
💬 Join us on Discord:
pracnet.net/discord
📜 More free CCNA resources:
www.practicalnetworking.net/i...
#ospf #ccna #hello - Наука та технологія
📌 *More free preview lessons from the Practical OSPF course:* pracnet.net/ospf
📌 *Want even more? Check out the full course:* pracnet.net/ospfcourse
📌 *CCNA Resources:* pracnet.net/ccna
📌 *Learn Networking:* pracnet.net/nf
📌 *Learn & Practice Subnetting:* subnetipv4.com
Never heard of any thing so clear, simple and valuable than this. Thanks
Cheers, Ahmed !
I'm a visual learner and this channel and lessons have really helped me in digesting several technical topics.
I really hope some company sponsors your content - I would buy something you mentioned just because you are such an amazing teacher!
Awesome video as well as the series too. Really helpful, easy to follow and understanding. Thank you so much.
You have an amazing teaching ability. Content is so well-organized, clear and concise! Thank you!
Nicely and clearly explain every pieces. your teaching methods it that much good that in a single day I watch more than 40 videos.
Ha! Awesome. Thank you. Glad you've enjoyed my content, Azad =). 40 videos! Wow, you've earned a break =).
Best OSPF area type explanation I ever read, especially for stub and NSSA. Thanks a lot for helping to understand the concept within 5 minutes!
Thank you for the kind note. GLad you enjoyed the video, Randy =)
I feel your series is even better than INE and Udemy paid program, that is really awesome work.
@@randyyihsienhan
I am finally be able to make a clear distinction between Stub and NSSA. Thank you very much
Awesome, Guy! Happy to hear that =).
Hell of a video series. Im hooked.
I would highly recommend it to everyone who is studying OSPF protocol.
Dude you're really good at this
Thank you =)
This is the best ospf details I have seen in UA-cam.. very good summarized, just waiting for BGP, QOS series.
Glad you've enjoyed it =). Hope you enjoy the rest of the videos in the series as well. ua-cam.com/play/PLIFyRwBY_4bSkwy0-im5ERL-_CeBxEdx3.html
Boy, do I like this training!
Sergio! I've enjoyed seeing your positive comments on the videos in this series =) Glad you're enjoying them!
Crystal clear content! Thanks
clear, concise and to the point
Awesome OSPF videos! Really useful and well explained. Thanks a ton for sharing!
You're very welcome, thank you for your support.
Great Lessons love the explanation !!!
Thank you for all your efforts you're doing Ed! I really appreciate these handy animations and your so simple way to explain that complex processes.
You can wrap it up like no one else ever did. I'm truly amazed!!
Thank you for the kind words.
If you're willing... Could you do me a favor? Do you mind sharing this video on Linked In, Reddit, Twitter, Facebook, or any other social media you use? As an independent creator, that would be an _enormous_ help, and I would appreciate it _greatly_ .
Awesome video, thank you for the knowledge.
I would be more than happy to support you in the future lessons and make it obvious for you that your work really pays off - trust me, it's just so much more pleasant to learn from your videos rather than some indian youtubers that barely understand the topic and try to speak it out.
*Once again, keep it up!*
Hi Stepan,
Thanks for the kind words =). I'd love to continue creating this content. The best way to support me is to share this content with any audience you think might benefit from it. Beyond that, I also have some courses you can purchase here: classes.pracnet.net/
Either way, thanks for the kind note. Glad you are enjoying the OSPF series!
Nice. Clean , direct, easy to follow and understand. Thanks!
You're welcome, Michael.
Great lesson, the way you break this down makes it easy for me to understand.
Thank you, Ed. Glad this is helping OSPF makes sense =). Don't forget to check out the rest of the OSPF lessons either: ua-cam.com/play/PLIFyRwBY_4bSkwy0-im5ERL-_CeBxEdx3.html
Awesome video series! 👏🎬
Glad you enjoy it!
best Networking teacher out there
Thank you for the kind words, Ohad. Cheers =)
Beautifully explained. Thanks
You're welcome =)
Dear Sir, you have very tactfully explained, but plz when you upload the video with multiple language so it is better to understand students.
Love your videos Ed. Your content and your approach to teaching is amazingly unique. Would love a BGP deep dive series
very perfectly explained.Thanks
Cheers =). Glad you enjoyed it !
Thanks for posting this video! It's easy to understand and your videos keep me motivated to learn more!
Awesome, glad to hear! Keep up the good work!
Excellent teaching.
Nice explanation!
Thank you finally concept is clear
Glad to hear, Pooja. Hope you enjoy the rest of the OSPF series as well: pracnet.net/ospf
@@PracticalNetworking sure I have started thanks😊
this series is very educational and sexum
Thanks for this Ed
You're welcome, Ursura =)
great video!
Great video, Ed. The way you break it down is great and makes it easy to absorb. The simple explanation of Area types has already helped more than most videos and I have seen a lot. Love the adjacency non match info too. Does the MTU need to match too or is that somthing else?
Hey Don. Thanks for the note. Glad you enjoyed this angle for Areas Types =).
The MTU one is tricky. In my labing I've found where the MTU mismatch causes a neighbor adjacency to fail, and other times where it doesn't. In any case, MTU isn't actually in the Hello Packets, it's in the DBD packets, so I didn't include information about the MTU in this video. (which honestly, already went much longer than I expected, ha!)
MTU should match per the RFC, but keep in mind how different vendors do/don't include ethernet header in the value, so it might be 4-8bytes different also with MPLS or other encapsulation.
This is a good treaching. Thank you.
You're welcome, Azza! 👋
thank you of the great content
Thank you very much 🙏🏻
Thanks so much for your help.
God bless you professor
You are very welcome
Awesome video sir
You're welcome, Karan!
great video
Cheers DNJ =). Thank you again.
You should make paid course for ccna , ccnp because you will the best trainer trust me
I think about committing to something like that all the time.
ed thanks for great explntion
You're welcome, Abidirahman =)
Muchas Gracias!
De nada =)
Thank you !
You're welcome!
Thank you !!!
Great , Thanks
You're welcome, Gihan.
amazing👏
thank you mate
Thank you
Great videos. Any plans to make a CCNP training series?
I've thought about it =). No plans at the moment.
@@PracticalNetworking CCNP series would be great, as I'm entering a university soon and am planning to catch up where I've finished in high school - CCNA :-)
Thanks 😊
Thanks!!
You're welcome =)
Holy moly!
amazing videos to teach network knowledge, would you make lesson for advance network like BGP, VXLAN, etc ?
Possibly, yes. BGP has come up a few times as a suggestion =)
Awesome, kindly if you have made any Wireshark packet analysis & any interview preparation I believe that will be helpful for many people :) Thanks
Thanks Ed, prefect visual explanation, do you have transcript of this series on your website ? cheers
Glad you enjoyed it, Chirag. I'm afraid I don't have a full transcript. A lot of the content of the first 5 videos has been converted to article format, if that is helpful:
www.practicalnetworking.net/stand-alone/ospf-training-course-free-m1/
@@PracticalNetworking thank you so much 🙏
@@devpatel2102 You're welcome =)
Thank you very much for the great videos. Helped me a lot on my job interview process.
Are there any plans for future BGP series? =)
Bravo
nice
Thank you, Priya.
Is Area Type part of the hello packet ?
As usual amazing explanation :) I recall reading that the Hello Packet does not explicitly mention the area type. Could you please confirm? Thanks
Lots of useful and interesting information, thanks! Some questions remain though:
~~- If the Hello Packet contains the sending router's RouterID and the list of neighbours, what new information does R2 in 12:09 have to send to R3/4/5 if only R1 has learned something new? R2's Hello-Packet would still look the same, no? Or are we simply talking of forwarding received Hello-Packets? If so, will the source IPs remain the same or will they be replaced by the relaying router's IP?~~ (forget that, that was LSUs, not Hello Packets)
- 16:00 matching of Hello Interval and Dead Interval --> Is this something that is enforced programmatically or is it just best practice? Also, how I understood 3:16 is that R2 tells R1 after what time R1 should assume R2 to be dead, which only needs to be more than the Hello-Interval in order to avoid flapping. No need for R1 to tell R2 the same numbers.
Good questions.
The new information wouldn't be contained in a Hello Packet, but in a LSU. The Hello packet would largely be the same. Remember, OSPF is about sharing routes, so in this context the "new information" is learning of a new route. Since R1 is not connected to R3/4/5, that new route must be propagated through R2.
Re Hello/Dead intervals is enforced programmatically -- the neighbors will not form an adjacency if they disagree on the hello/dead timers.
While I see your point that it _could_ work without an exact match... the creators of OSPF decided to require an exact match. Hence, this is the rule enforced programmatically =).
thank you for this great explanation but i have one question why would we interconnect more than two router via a switch ?
I would say it's pretty rare... but it _could_ happen, therefore OSPF has to account for it.
I´m leaving a comment to help your stats because your videos are excellent, you´re hot. Your voice is clear as well. The lessons well thought out.
Thank you for supporting this channel, and the kind words =).
hello gtreat guy
👏👏👏
Cheers!
Salaama
Very great explanation!
I have two questions:
1)
10:30
Is it 80 or 81 route on NSSA? 50 from RIP, 10+10+10 from OSPF (total 80) and then how do we reach EIGRP? Is it +1 from default route (total 81) or is it 1 route from Area 99 that goes to EIGRP?
2)
14:23
Does DR & BDR election happens on every multi-access link or election happens per area?
Thus, one area have only 1 DR and 1 BDR or can it have multiple, because there are multiple multi-access links such as Ethernet?
Thanks for the video!
Good questions!
1. It's 80 by default, and then you as the Admin can choose how to apply your default route. OSPF itself, however, would only account for 80 routes.
2. The DR/BDR election happen for each multi-access link. You can absolutely have many DR's in a single area (you'll always have one per multi access link).
Cheers!
@@PracticalNetworking alright, thank you for your answers!
An MTU and link types also have to match to get an adjacency. Very often, this is overlooked (especially in multi-vendor projects), and
Yea, great point. I went back and forth about including this, but opted against it since the MTU isn't shared in the Hello packet, it's only shared in the DBD packets.
It's a point I plan to circle back to later in the series.
Is what is meant by the default path...a path that works using the Static Default Routing Protocol?...or what is it intended...help please...and thank you for your excellent explanation
I don't think "default path" has an objective/absolute definition. It likely context based.
-- the default path OSPF uses
-- the default path from the default route
-- the default path towards the internet
etc...
@@PracticalNetworking But does this default path make the stub area able to send and receive data from the area that has a protocol other than OSPF??.... And how can this default path reduce 30 paths or networks to one path or one network, as you explained In the example??...Does OSPF say that the paths are converted to one default path automatically once I make the “Stub Area” or do I configure it manually?......and Does the default route exist on the topology table of the ABR router only?.... and Thank you for what you do for us🤍
Sir, are these available on Udemy, would be great to have them there as well. These series are great learning.. thx
Not at the moment =)
hy ! actually i have got a doubt that area is basically used to restrict the domain of the lsa's so that means area 88 is going to have 10 routes right ? but when area type is normal its becoming 30 how ?
The answer to your question is in the Areas video:
ua-cam.com/video/CM9BlFHB3q4/v-deo.html
Basically, even though the route is in another area, each area still needs to know about the route (so it can send packets to that area). The area boundary limits the propagation of _unnecessary_ changes if they occur in a foreign area. More details in the linked video.
At 10:52 if the default route for area88 was R5, then neither R5/R6 would be able to reach the 100 EIGRP routes behind R7, no?
Hello Sir .... I have gone through you networking fundamental MODULE 1 course and I am interested to buy the entire course . Kindly let me know how can I procure it. Thank you
The Networking Fundamentals course hasn't been created. I'm waiting to see how much reach Module 1 gets before committing the time / energy to create the full course. The best way to make it a reality is to help spread the word about the free Module 1 videos.
BGP ?
teach bgp！！！
Thank you !
You're welcome!
Thank you
You're welcome, Hussain.