Designated Router // Backup Designated Router // DR BDR Election // Practical OSPF // Lesson 6
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- Опубліковано 3 сер 2024
- The Designated Router (DR) and Backup Designated Router (BDR) exist to reduce redundant LSA flooding on an OSPF multi access link. Routers on a multi access link use the 224.0.0.5 and 224.0.0.6 Multicast IP Addresses to efficiently share LSAs with each other.
In this video we explore the process by which a DR and BDR are elected. We discuss the WAIT interval in OSPF, we discuss Preemption and Priority numbers. We wrap up the video by showing you the sequence of events that occurs when a routing update needs to be sent on a link with a Designated Router and Backup Designated Router.
This is Lesson 6 of the Practical OSPF series:
• Practical OSPF
00:00 - Intro
00:11 - DR BDR - Review
01:26 - Electing Process: DR, BDR, and Drothers
06:14 - Neighbor Adjacency Process - Full or 2-WAY
08:29 - DR / BDR / Priority are Per-Interface, not Per-Router
09:06 - Deterministic Designated Router by setting Priority
12:07 - Routing Updates from DR, BDR, and Drothers - 224.0.0.5 - 224.0.0.6
15:27 - Packet Capture of OSPF DR BDR Election Process and Routing Updates
💬 Join us on Discord:
pracnet.net/discord
📜 More free CCNA resources:
www.practicalnetworking.net/i...
Packet Capture:
ln5.sync.com/dl/ea7838d80/itq...
#ospf #ccna #neighbors - 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
Packet Capture of everything we discussed in the video:
ln5.sync.com/dl/ea7838d80/itq4upcf-5vhir39u-pwkpdaum-daehr52t
Love your videos Ed. Your content and your approach to teaching is amazingly unique. Would love a BGP deep dive series
A really sharp presentation with great schematics. Thanks a lot!
Super helpful DR and BDR guide! Thanks for the clarity!
Thank you for supporting the channel =)
Hi Ed, writing first time comment for any instructor, your way explanation is outstanding very clarity on every topic . You have made my journey to become network engineer very smooth love from me and Bharat.
Thank you for the kind words, Ankit. Glad you are enjoying this series.
most complete and clear video of networking I've seen. Thank you very very much. I appreciate it a lot
Glad you enjoyed it, Rocio.
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_ .
I never knew or heard that about the DR interface over DR router... hmmm ....you shld be the GOAT of YT
You explain it so well. Thank you for including the full playlist and adding more info . Very much needed.
You're welcome =)
i have been searching good OSPF video but now i blessed ..
Thank you for supporting the channel! Glad you're enjoying the content !
Thanks sir for your teaching. You are the best teacher ever found.
Thanks a lot. this is the most easy and complete explanation of the DR/BDR election process.
Cheers, Anis. Glad you enjoyed it. That was my goal with the video =).
Hope you enjoy the rest of the OSPF series as well: pracnet.net/ospf
You make studying so much easier thank you so much I love your content
Glad you're enjoying it, Ohad.
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_ .
Was desperately waiting for new video in ospf playlist, as always mesmerizing Ed!
Glad you enjoyed it, Karan! I just finished editing next week's video, so expect another one on Monday =)
@@PracticalNetworking That;s awesome Sir! 😃
Simply amazing explanation Ed!!! Many thanks and appreciate your efforts!! It would be great if you could prepare such series on all the topics.!!!
Very detail-oriented explanation. Thanks
You're very welcome, thank you for supporting the channel.
Ed is a legend. Networking concepts are so dry, intricate and hard to grasp from books and videos because many instructors do not go into grassroots. I’ve never seen an instructor explaining it going into the weeds. I appreciate Ed’s work in having this level of clarity on networking concepts. It is very hard to get to this level. Respect 🫡
Thanks for the kind words, Gnanadeep, had a rough week and this cheered me up to start the weekend.
I love your videos. Please do a BGP series.
Excellent description of the election process!!
I just get my ENCOR certified, now i will go for the ENRSI, this videos help to understand more details. Thanks.
Always a top notch. Although I’m no longer in a networking role, I’ll continue to stay up to date. Thank you!
No longer in Networking! Where are you now?
(Glad you enjoyed it and thank you for keeping up with the channel)
@@PracticalNetworking I recently took on a role supporting healthcare applications where configuring net-gears is not in scope. I do have a voucher for CCNP which I’m going to try out for later this year, so your blog and UA-cam will be a source of knowledge. Thank you again for everything!
@@enes.7720 You're welcome Enes, thank you for all your support.
this video is worth a million likes (or more) ... I've been struggling with the docs trying to understand the election process. Your explanation is crystal clear. Many thanks for this excellent job
Love your content.. I am glad I got to learn OSPF from you! Please keep going forward.. I would love to learn BGP from you as well❤️
You make studying so much easier, thank you so much
Very Useful.
well explain , easy to understand for beginners
This series helped me a lot. Thank you
Excelente explanation! please more videos about other routing protocols also their redistribution. Thanks a lot for this famous great help!
NOted Mohand. Glad you enjoyed this.
Ed, well done.
Thank you =)
God level TEACHER!!!!!!!!!!
Thank you ❤
Thank you for making very easy video to follow.
You're welcome, Graham. Cheers.
Great Job!!
Quite remarkable.
=)
BROOOO... you earned my Subscription... Awesome explanation.
Thank you for your support =)
Thanks again. Great explanation.
great explanation
Thank you again, DNJ.
this series is very educational and sexum
Loved it! thank you.
You're welcome, Mock =)
Good information with practically ...thank u bro.....keep it up
You're welcome, Mandala. Glad you enjoyed it =)
Well explained thanks Ed
Thank you, Abdirahman.
Really useful, thank you
You're welcome, James. Cheers.
Excellent
My cats thank you for your videos 🐈🐈👍👍
Nice job
nice mate thank you.
great job
Wonderful
Thank you 😊
I got a lot of more than CCNA level Ed thank you
Indeed =)
Thank you Sir..
Thank u ❤ that was helpful
Great 🙂
this is just amazingggggg!
Thank you for supporting the channel =)
Nice!
Awesome
It'd be great if you could do a series on Route Filtering
This is so so smooth and easy to understand
Can you please make a video for MPLS?
MPLS is going to be behind BGP, which is behind a few other projects, at the moment =/ . But yes, that would be fun . Glad you enjoyed the OSPF series.
This is such a great serious! I hope you keep it going. I would definitely be willing to pay for this!! Do you have an EIGRP series in the works? This is helping me so much with CCNP Ent
Hi thanks for the kind words =). Glad you are enjoying this series. I'm releasing Lesson 11 Monday!
I don't have a video series covering EIGRP, but I did write three articles on EIGRP:
EIGRP Explained : www.practicalnetworking.net/stand-alone/eigrp-terminology/
EIGRP Metric : www.practicalnetworking.net/stand-alone/eigrp-metric/
EIGRP Feasibility Condition: www.practicalnetworking.net/stand-alone/eigrp-feasibility-condition/
That said, if you are willing... could you do me a favor? Do you mind sharing this video series 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_ .
nice
Rockstar! I wonder if you could also do similar lessons on vrf, MPLS, BGP as well. I have been looking for just these types of lessons.
Glad you've enjoyed these. BGP is on my list for sure =) But I need to finish a few other projects first.
DB/BDR Status is per Interface, so, for this topology per VLAN
Yes, per interface. So if you have vlan separated "sub interfaces", then it's per sub interface
i have a doubt here ED that " when a drother gets an update it first sends out the update to multicast address 224.0.0.6 that means only dr and bdr will receive this update, after that dr will forward the update to 224.0.0.5 that means all the routers present in the link will receive it. so at this point it seems like bdr and the drother who leads the update initially, they get the update again which is unnecessary, which may result lsdb flooding. i think it should not be occurred!!! or if there any other reason for that then please clear my doubt!!!!!!!
Just wondering, is there a link for the full series for CCNA. I know that there are a lot of play lists for different CCNA topics, but wondering if there was on grouping all the topics for the exam. Thanks a lot for the effort.
I don't have a full CCNA series at the moment, but it is something I consider doing almost daily (seriously!). In the mean time, most of my CCNA content is posted here: pracnet.net/ccna
Cheers !
great teach why dont add the other bgp, eigrp,
Hi Ed, if I had initially set different priority numbers on the routers and then reboot the routers, would the first router to come up claim DR when it has a low priority number (when not the highest priority number router)?
It depends if the reboot finishes before the "WAIT" timer expires. Remember the routers come up and first spend some time waiting to see what other routers are out there (same duration as dead interval). If they finish their reboot 10~ seconds apart, but are still within the 40~ second wait timer, then they will see each other's configured priority and the DR/BDR will follow what you configured.
@@PracticalNetworking thanks
What I'm missing in the video is, how long would each router wait for hello packets from other routers before starting to advertise a DR and BDR router? Say we reset the OSPF process on all 4 routers at the same time, R1 sends hello packets and receives the first hello packet from R2, does R1 instantly decide that R2 is the DR, if it hasn't received the hello packets from R3 and R4 yet?
I think I found the answer myself, the wait timer also applies in case the router does receive hellos from other routers. It will still wait for the duration of the wait timer for other hellos before starting the election.
Yup, nailed it. The WAIT timer is how long they will wait to see if a current or better DR exists, if not they will elect themselves DR (or BDR). I mentioned this at about 2:40 in the video =). CHeers @@daancelie3400
Another Q, please. Where in the neighbor adjacency states will the DR/BDR election happen?
It happens in the 2-way state. This is what I referred to in the video as the routers deciding if the adjacency will proceed from here.
More details here: ua-cam.com/video/X0OBAPc3dpM/v-deo.html
@@PracticalNetworking Thanks
The DROTHER /DR/BDR states are per Area ? meaning are these states based on the area or the interface ?
Per interface =) See 8:29 in the video
I am familiar with the function of OSPF, however, I have never configured it and am certainly not knowledgeable in it's full capabilities. Our network is mostly made up of layer 3 switches that act as gateways for various VLANS. We are planning to replace one of our Juniper stacks with a Cisco stack. I think we have VRRP configured on the new and old switches to visualize the gateway IPs, however, we are wondering if it even possible to have both switches online and servicing downstream devices while both handle the same networks. Is this possible? If so, can you suggest some tips and reading links to learn how to do this properly?
Thanks
This almost sounds like a consulting question... you're welcome to try in my Discord, but certain levels of service would require a consultation agreemtn.
Hi sir.. When all the router restarts R2 should come as DR not R4.. since BDR is already elected. Am I correct
Just a doubt ...
You said that whichever router participates first in the election becomes DR ....
Then what's the use of Priority ?!
so in the end... It all depends on who got to turn on first..? if there a command that will force all router in 1 area to do re-election :/ that would be much easier ngl 😂
Yes, many times, this is the case =).
There isn't a command I know of that forces all the routers to re-negotiate the DR.
how can I join your channel?