[c-nsp] OSPF area design question

[Marcel Lammerse]

Thank you (all) for your suggestions. They've been most helpful. I'll 
go with the option of having 4 (e.g. area 0,1,2 and 3)  areas in total, 
instead of having multiple areas that are not really beneficial.

Kind regards,
Marcel

On Aug 31, 2004, at 4:48 PM, Howard C. Berkowitz wrote:

> At 9:14 AM -0400 8/31/04, Peter van Oene wrote:
>> At 04:41 PM 8/30/2004, Dan Armstrong wrote:
>>> We too have a similar situation.  We opted to make a whackload of 
>>> OSPF areas. I am very curious if this design is going to eat up some 
>>> resource
>>> unnecessarily.
>>>
>>> I can't quite figure out why in a "real"  NSSA scenario that other 
>>> routers in
>>> the same area need to know anything about other routers in the stub 
>>> area,
>>> since the only path anywhere else is up to the distribution layer 
>>> anyway,
>>> which is handled with the default route that gets advertised down...
>>
>> spf comes to mind.
>
>
> SPF is obviously a consideration, but another consideration: does the 
> NSSA have more than one ABR? If so, the other routers do need to know 
> about it so they can pick closest exit.
>
>>
>>
>>> Dan.
>>>
>>>
>>>
>>> On Monday 30 August 2004 16:37, Marcel Lammerse wrote:
>>>>  Ok, if you have that area 1 with 15 routers. Would it be a good 
>>>> idea to
>>>>  keep them all in one area, or would it make sense to assign 15
>>>>  different area numbers and make each of them a separate area (NSSA 
>>>> in
>>>>  this case). Because, I figured, an update from one of the router 
>>>> will
>>>>  be flooded throughout the entire area which is totally unnecessary.
>>>>
>>>>  I like to know whether the extra configuration and administrative
>>>>  overhead is worth saving on unnecessary update floods and cpu 
>>>> cycles
>>>>  processing them.
>>>>
>>>>  On Aug 30, 2004, at 9:47 PM, James Hampton wrote:
>>>>  > The way I'm reading this is that you have three hub routers 
>>>> connected
>>>>  > like  points on a triangle, with each point having 15 or so 
>>>> spokes? If
>>>>  > this is the case I would make the top router(or the one in the 
>>>> middle)
>>>>  > area 0 and the others 1 and 2 or what ever numbering scheme you 
>>>> come
>>>>  > up with. Than address each area with contiguous blocks so that 
>>>> you can
>>>>  > summarize and keep the routing table as small as possible. The 
>>>> spokes
>>>>  > could be "stubby" sense they have only one way out.
>>>>  >
>>>>  > James
>>>>  >
>>>>  >
>>>>  > On Mon, 30 Aug 2004 17:54:35 +0200 (CEST), Marcel Lammerse
>>>>  >
>>>>  > <lammerse at xs4all.nl> wrote:
>>>>  >> Hi,
>>>>  >>
>>>>  >> I have a hub-and-spoke network, for which I'd like to use OSPF 
>>>> as a
>>>>  >> routing protocol. The spoke sites will advertise their networks 
>>>> to
>>>>  >> the hub and receive a default route from the hub.
>>>>  >>
>>>>  >> A common piece of advice in OSPF design literature, is to use
>>>>  >> different
>>>>  >> area numbers to prevent unnecessary LSA updates from flooding to
>>>>  >> routers
>>>>  >> that don't need the updates and to avoid the cpu processing 
>>>> overhead.
>>>>  >>
>>>>  >> The total network has some 50 routers.  There are 3 
>>>> inter-connected
>>>>  >> hubs
>>>>  >> and some 15 routers per hub. The way I see it, I can do two 
>>>> things:
>>>>  >>
>>>>  >> 1.      assign a lot of area numbers to prevent the LSAs from
>>>>  >> propagating
>>>>  >>        through to routers that don't need them. However, this 
>>>> leads
>>>>  >> to a
>>>>  >>        relatively complex configuration.
>>>>  >>
>>>>  >> 2.      accept the, potentially small, bandwidth waste and 
>>>> don't care
>>>>  >>        about the cpu overhead (we're talking 2600XMs here).
>>>>  >>
>>>>  >> Option 1 just doesn't seem worth it. Could someone provide some
>>>>  >> advice,
>>>>  >> experience or tips?
>>>>  >>
>>>>  >> Thanks.
>>>>  >>
>>>>  >> -Marcel
>>>>  >>
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---
"..the price to pay for teenage sex is pretty high--
unwanted pregnancy, disease, and ending up with one ear
bigger than the rest because it's always cocked toward
the door in case the parents come home early."
										- Michael Moore