[c-nsp] Separating internal/customer routes into IGP/EGP

[Jee Kay]

I keep seeing people on here and other places recommending that your
IGP should only ever carry your internal routes (loopbacks, transfers,
etc) and you should run something like iBGP to carry customer routes
that you learn/inject/blah.

I've been trying to figure out how this would work from an
implementation point of view and am coming up a bit short...

Our typical infrastructure from CPE to core looks something like

CPE--PE Aggregator--L3 Firewall (OSPF and BGP speaker as necessary)--Core

It seems to me that running iBGP meshed would be pretty much
unfeasible for this sort of setup due to the sheer number of devices
that end up getting involved. My next thought is using a pair of core
routers as route reflectors, but even that doesn't seem to be
particularly tidy.

How are people doing this in real life?

Thanks in advance,
Ras