From everywhere to everywhere in spatial network

ArcGIS Network Analyst question:

I have a network dataset representing an archaeological site with ~500 buildings. Each doorway of these buildings represents a terminal node. I would like to simulate aggregate foot traffic patterns at the site.

One way to do this would be to generate least cost network paths from every node to every node. That is, generate 500 x 500 route matrix (250,000 routes). That is the same as doing a closest facility analysis for every building at the site. Of course, manually doing a closest facility analysis 500 times would be ridiculously time consuming. I can't see a way to do it using Model Builder. But perhaps there is a way. It's not a complex workflow. Any advice on how to script it?