06-13-2024 05:54 PM
Hi, which one for best design for OSPF Area?
06-13-2024 06:11 PM
It would depend on additional information.
BTW, is there an area zero for option 3.
06-13-2024 08:05 PM
what does your exam dump says?
06-14-2024 02:04 AM
since Hub use point to multi-point interface then this make hub and spoke need to be in same Area so option 3 is never be correct
Op1 I recommend alot but compare to op2, op2 is more better why
ospf have one limit that the summary or any filter can not be config in any internal router (internal meaning router all interface connect to one area) so we need to make router ABR or ASBR to get some filter and summary
op2 vs op1 the hub router is ABR so we can summary and filter some prefix send to other spokes.
so in end
OP2 is 100% is correct answer
MHM
06-14-2024 06:41 AM
"since Hub use point to multi-point interface . . ."
Oh? You know this how?
I've used hub topologies with p2p links.
You're assuming the "cloud" enforces a single network? Some do, some don't.
This is one of the reasons my prior reply had additional information is needed.
The problem with option 3, it doesn't show an area zero, and without area zero none of the non-zero areas would know of the other area routes.
However, if core router had a loopback interface in area zero, it would work fine.
This is why I questioned area zero existence for option 3.
Regarding the rest of your reply, you're 100% correct about route filtering/summarization on an ABR but is this really needed for one LAN (?) network? I.e. there's overhead with areas.
Practically, I would chose option 1 over option 2, but for an text book answer, for the reasons @MHM Cisco World describes, option 2 would be considered better than option 1.
Option 3, as shown (without an area zero) wouldn't work correctly.
Assuming there is an area zero for option 3, which is better option 2:or 3?
There are pro and cons for both. My guess would be, the "book" would prefer option 2 as it distributes ABR processing. Personally, though, I'm not a fan of running area zero across WAN links, as they often are less stable.
But, in real world, for a network so small, I would likely just run a single area logical topology.
In real world, though, I would take into account other factors, so again, without such information, cannot say what's the best area design. This is an "it depends" kind of question.
Like @johnlloyd_13 I too would be curious to the "book" answer and its reasoning.
06-14-2024 06:44 AM
Oh? You know this how? <<- I am MHM so I know that LOL...
MHM
06-14-2024 06:47 AM
Laugh.
06-14-2024 07:06 AM
in Hub one interface use to connec to multi spokes
so this interface is P2MP
this interface have only one IP (usually the tunnel IP)
if we run different Area in each spoke then we receive hub interface for which area will config ? the interface need to config to only one area
that why Op3 never be correct
MHM
06-14-2024 08:16 AM
Hello
Looks like the cloud would not be under your control meaning the other 2 options you don’t have the control of the backbone area (0)
Option1 would be the best option here-- Each non BackBone area can become stubs area thus reducing the OSPF database drastically at each site/area, additionally if each of those stubs areas need to advertise external routes they still will be able to.
06-14-2024 09:26 AM
Laugh (not at @paul driver or the others) but what seems like a simple question obtains difference responses.
The reason for that, I believe, is due to lack of information. Much can go into whether an OSPF multi-area should be deployed, and if deployed, how it should be structured.
Even with all the information possible, it's possible more than one topology design might be considered the best possible. Or, laugh, in the real world, sometimes "best" is whatever the lead engineer or engineer manager prefers. ; )
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