multihoming without BGP

I had to jump in here with a correction and clarification. We are using
Netscape Enterprise Server 2.0. The 'software virtual server' feature
doesn't work with any version of Netscape Navigator up to and including
Communicator Preview 5. The server sees a HTTP 1.0 not HTTP 1.1 request.

Getting a Host: keyword as part of a request is really a protocol violation
if the browser said HTTP/1.0 rather than HTTP/1.1. But all browsers do this,
except Lynx, and any reasonable web server (Apache and Squid, for examples)
will let you switch web roots based on the Host: keyword, regardless of HTTP
versioning. It's possible that all you have to do is switch web servers and
your need to burn address space will evaporate immediately.