[c-nsp] Latest iteration of core upgrade - questions

[Rick Ernst]

I've posted a few times over the last few months regarding general equipment
choices for a core upgrade and I'm looking more into design validation and
gotchas, now.

Recap/summary: border/core/aggregation design with A/B
redundancy/multi-homing at each device. 7206VXR/G1 on the border as media
converters and BGP end-points, dual 7507/RSP16 as the core and
route-reflectors surrounded by a dual layer-2 sandwich, with various devices
for customer aggregation below that. The 7507s and layer-2 glue would be
replaced by a pair of 7600s.  OSPF as the IGP.

A new wrinkle has been added to the mix and that is a local ("across the
parking lot") facilities expansion and a remote facility that is turning
into a POP as well.  The local facility has dozens of strands of fiber
available. The remote facility  has 4 strands (A/B, as well) and also lands
an upstream provider, backhauled to our existing facility.  As part of the
redesign, I need to make at least the new/local facility able to stand on
its own for DR purposes.

The consensus I've seen for core routing/switching equipment is 7600s with
Sup720-3BXL and various line cards.  I'm curious how integrated the
switching fabric and routing engine are; e.g. if the switch fabric is
provisioned and there is a Sup failure/failover, will the switch fabric
continue to forward layer-2 traffic? Additionally, if there are a group of
ports provisioned in a VLAN, will the VLAN continue to forward layer-2
traffic even if the SVI is down?

>From a design perspective; I could extend layer-2 to the new local facility
and use the existing facility for all routing and transit.  This doesn't
give any stand-alone survivability to the new building, though.  I can swing
telco/upstream entrance for one provider to the new building, but still need
to integrate the layer-3 and IGP.  Ideally, I'd like to slow-start the new
building without redundant cores and use the existing building for
redundancy. I'd also like to use the new build as a template for future POPs
where "lots of fiber" may not be available.

I've considered having each building/POP as a BGP confederation, and also
iBGP peering at either/both the core and border layers (with appropriate
meshing and/or route-reflectors).

Am I going down the right path?  Pointers to additional information?
Additional considerations I haven't mentioned?   Cisco's _Internet Routing
Architectures_ and some other Cisco Press books are getting a workout, but
I'm not getting a good feel for my particular situation.

Thanks for all the help; past and future!

Rick