OSPF Professional Lab 1

Lessons Discussion
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This topic is to discuss the following lesson:

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Thanks for your sharing this lessons and I hope the next topic will be L2 lab. It’s the most important topic for networking learning. Thanks.

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Thanks, big fan of this! :slight_smile: Would love to more of these, maybe covering L2 or EIGRP

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Hello Niclas

Thanks for the feedback, we do our best! More labs are on the way, thanks for your suggestions!

Laz

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AMAZING LAB!!! Can we please get more of this? Possibly a mix of everything as well like EIGRP redistributing to OSPF with some BGP DMVPN etc… Fantastic lab!

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Please establish a typical Enterprise lab that would be very helpful if you describe along with that.

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Hello Sahakt

Thanks for your feedback! We’re thrilled that you found the lab useful. We are planning on putting together some more labs in the near future, so stay tuned for those! Thanks for your suggestions, we’ll take a look with Rene and see what we can do…

Thanks again!

Laz

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Hello Mohammad

Thanks for your suggestion, we’ll consider it as we discuss the next labs that we’ll be creating.

Keep labbing!

Laz

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Thank you very much. Could you please do the same for BGP? This topic is much anticipated and would be extremely useful to many of us.

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Hello Asif

Glad to hear that you find the lab useful. We’re working on creating more of these types of labs, and BGP is definitely on our to-do list. Thanks for your feedback!

Laz

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Hello ! i’ve completed this fantastic Lab. I’d like (and appreciate your effort & time ) more labs like this, for BGP, EIGRP and so on…

Regarding this Lab i have a doubt about the following :

when summarizing area 2 routes on ABRs R3 & R7 i think is a very specific scenario because discontinous area 0 and to overcome this establish a virtual-link between R3 and R7.

So, when i did the Area 2 summarization i only did it on R3 and then figured out it didn’t take any effect because i still saw the more specific prefixes instead the /22 pfx ive summarized. It took effect when i also did this same summarization on R7.

It was a little tricky because the discontinous area 0 but if both R7 & R3 were “parallels” ABRs in Area 0 (non discontinous) i’d be more obvious (at least for me) i have to do the summarization on both routers.

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Hello Juan

We’re glad you liked this lab! We’re working on more labs, and in the near future we’ll be publishing them! We’ll keep you posted!

Yes, that’s exactly correct. The summarization has to be applied to both R3 and R7 otherwise summarization will not occur. This is because of the fact, as you correctly stated, that we have a discontiguous Area 0, and R3 and R7 are both ABRs with Area 0.

The same thing would happen if you tried to apply summarization on R2 and R4. These two routers are ABRs and both connect to Areas 0 and 51. If you apply it only to one of the two routers, the summary routes will not appear.

You know why? Because a more specific route is always preferred over a less specific route. So if one ABR injects the less specific summary route, and the other ABR injects the more specific individual routes, routers within the area will prefer the more specific routes. Does that make sense?

I hope this has been helpful!

Laz

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Hi,
I found the below instruction on Section 3.4.2 Load Balancing and Path Preference
"To achieve this, consider changing the type of stub that Area 51 is configured as. Do not remove the stub configuration completely."
But we are not configuring Area51 as a stub area, I am getting confused on this.

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Hello Arijit

Actually, if you look at section 3.3.3 Area 51, you will find that it states that Area 51 should be configured as a Totally NSSA. So the statement you shared in your post is referring to this fact. Does that make sense? Let us know how you get along, and if you have any other questions, we’re here to help!

I hope this has been helpful!

Laz

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Hello,

Thank you for the lab, it’s good for practice.

However, in the configuration of area 51 you state that R5 must have a static RID with a value which can make it DR on the links with R2 and R4 (part 3.3.3).

In the solution (part 4.3.3.2) you say, about the choice of the static RID, “Note that the router ID you choose can be anything as long as it is of a lower value than the router IDs of R2 and R4” , and you pick RID 1.0.0.1 in your example. I’m sorry, but i think that it is false. To be chosen as DR, R5 (if all priority of all router’s interface are the same) need to have a RID with a higher value that the others candidates, not a lower value (quote from OCG CCNP ENARSI : “If the OSPF priority is the same, the higher RID is more favorable”. So 1.0.0.1 in your example can’t achieve this goal here, and R5 will be BDR and not DR on the two links.

Please, tell me if i’m wrong and i missed something. Otherwise, you should correct the lab solution.

Note : English is not my native language, I apologize if there are any grammatical or spelling mistakes.

David

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Hello David

First of all, your English is just fine, if you hadn’t mentioned it, I would not have realized it’s not your first language, so no worries!! :blush:

As for your comment, you’re absolutely right! The configured router ID should be higher than that of R4 and R2 so that R5 can become the DR, and that was my mistake. The results shown in the lab are those that would result from R5 becoming the DR, so the rest is OK.

I’ll let Rene know to make the appropriate corrections. We can use an explicit router ID of 10.0.0.1 for example, or any value that is larger than the router IDs of R2 and R4, and that should resolve the problem. Thanks again for pointing that out!

Laz