This is written up at Two-node setup with overlapping client subnets (http://kb.linuxvirtualserver.org/wiki/Two-node_setup_with_overlapping_client_subnets). The purpose of this setup is
This setup solves the challenge of serving remote users that originate from multiple different sites that all use the same overlapping subnet, all on a single pair of nodes. It also maps each remote site to a unique IP range so that users can be identified in application logs, etc. So in short, it combines a two-node, multi-interface lvs setup with network remapping. It's ultimately a fairly complicated puzzle.