>>Do you have an example for this scenario? A diagram would make it easier to
>>analyze. Also, I think one implicit thing here that's worth made explicit is
>>what we mean by a single failure in the FRR fundamentals. Case 1: it is a
>>single failure per complete set of areas. Case 2: single failure per area. It
>>seems that reducing to case 1 may make things simpler.
> I hadn't gotten to considering case 2; I'm still on case 1.
> Here's an example. In this case --- are area 1 and **** are area 2. S is
> connected via a virtual link to ABR1 in area 1 and by a virtual link to
> ABR2 in area 2. Y isn't connected to the backbone; it could also have
> virtual links in the two areas to ABR1 and ABR2 if needed.
> 10 1
> [ A1 ]-----[ S ]*****[ P2 ]
> | | *
> | 5 | * 1
> | | 1 *
> 10 | [ P1 ]-----[ Y ]
> | | *
> | 5 | * 13
> | 5 | *
> [ABR1]----[ B ] [ ABR2 ]
> | |
> 10 | | 10
> | |
> Summary Prefix 1 Summary Prefix 1
In this scenario, assuming the failure is that of P1 node, Y would lose its
connectivity in area 1 completely, wouldn't it?
>>How about we look at it this way: what we're interested in is protection,
>>whether this is ECMP or LFA. Removing increased memory consumption from
>>consideration as something we'll have to deal with anyways: if an
>>is constrained to support N next-hops only, and all of the slots for a
>>taken, well then one option is to not install LFAs at all--the route is
>>protected with ECMP after all. Should the topology change such that some slots
>>become available--one can add LFAs there.
> True - but the ECMP may not give protection in the multi-area paths.
I'm sorry, I'm not sure I understand correctly what you mean here. Could you
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