XEN with routed DomUs
Aus Markus' Wiki
With a reference to Martin Würtele:
Configure /etc/xen/xend-config.sxp for routing: (network-script network-route) (vif-script vif-route) and enable arp proxy with sysctl -w net.ipv4.conf.eth0.proxy_arp=1 for runtime and by adding net.ipv4.conf.eth0.proxy_arp=1 to /etc/sysctl.conf permanently.