multiple servers with 1 internet connection and fw

[g <wangw () singnet com sg>]

Greetings,

If I have a few Internet server machines (running different
applications) and each server is using one dedicated Internet connection
and firewall, it is logical to combine all of them into a singel
internet connection and use a single firewall to protect them. The
requirement is different internet server machines should be separated
from each other.

So there are basically two kinds of design, one is using multiple
network interface on the firewall so that each internet server machine
connects to one firewall interface. The problems for this are
scalability and performance. The other way is to use routers (or switch)
to separate each internet server and connect routers/switch to the
firewall, so the firewall will only have 2 interface, one external and
one internal (connecting to routers LAN or switch), the routers / switch
will be configured to disable traffic among them.

Any comments on these two options and your experience on any of them
will be most helpful. Any other way of doing this? Thanks.