You can layer the e-smith machine between the router and the hub. The e-smith box needs to have dual NICs of course. You just configure the e-smith box to point to the router, the router points to your external gateway.
At home, I run an e-smith server inside the router as just another machine on the network. E-smith should be configured in server mode, not gateway mode, and the router needs to be configured to route port requests to the e-smith boxes internal IP address, as appropriate.