[c-nsp] Hierarchical Route Reflector

[Thomas Bowlby]

Looking for guidance regarding deploying dedicate route reflectors
that will not be in forwarding path for traffic.

These dedicated route reflectors will be connected to our core network
and curious to see what people are doing in this case to prevent RR to
be used as a transit network.

I currently see two options for configuring ospf:
option1:infinity metric (max-metric router-lsa)
                pros:ease of configuration; creates a 'stub'
router-effectively advertising router-lsa with metric 65535
cons:full OSPF lsaDB (i.e increased convergence time due to size of lsaDB)

option2:stub area
                   pros:removes type-4/5 external LSA's from the lsaDB
and infinity metric is applied
                   cons:complexity added to ospf design/configurations

*To note we currently carry (working on adjusting) a large amount of
type 4/5 LSA's in our db at one pop, which seems removing these from
tables may lessen cpu time needed to converge quickly.  I’m also not
sure what the time delta would be between option1 & 2).

Thank you,
-tom