likewise, "FIB table growth" isn't yet a problem either - generally that just means "put in more SRAM" or "put in more TCAM space".
IPv6 may change the equations around .. but we'll see ..
IPv6 will someday account for as many IPv4 networks as would exist then, and IPv6 prefixes are twice as large as IPv4 (64 bits prefix vs 32 bits prefix+address, remainder 64 bits addresses on IPv6 are strictly local), so despite a 3x cost increase (1 32 bit table for IPv4, 2 for IPv6) on memory structures and 2x increase on lookup engine(2 engines would be used for IPv6, one for IPv4), the same techonology that can run IPv4 can do IPv6 at the same speed. As this is not a usual demand today, even hardware routers limit the forwarding table to the sum of IPv4 and IPv6 prefixes, and forward IPv6 at half the rate of IPv4. Rubens