Gianluca,
> I have read that an inter domain router (connected to the big Internet) has a
> routing table with 42000 entries (this value refers to the end of 1996).
That number is really old. This is what I see right now:
br7.amsterdam>sh ip bgp sum
[...]
68413 network entries [...]
[...]
> I would
> like to know if it is possible to estimate the number of entries of an intra
> domain router (that has only the knowledge of the destinations of the domain it
> belongs to).
When you do default routing (aka non default free routing) it entirely
depends on the size of the domain. For a stub network this could
typically mean just the address space of the customers.
__
Erik-Jan.
