I have a very specific problem, building a Linux VPN endpoint (with external VPN Gateway), which should route certain networks over the tunnel, others via default gateway. The Linux VPN should do a NAT on the outgoing connections for the VPN peers. Setup is as following: Internet gateway LAN 192.168.25.1/24 VPN Gateway LAN 10.45.99.2/24 (VPN tunnel 10.45.99.1 to net 87.115.17.40/29, separate connection to Internet) Linux VPN Router eth0 192.168.25.71/24 eth0:503 10.45.99.1/24 Default 192.168.25.1 route to 87.115.17.40/29 via 10.45.99.2 (send_redirects disabled, ip_forward enabled) Linux clients (multiple): eth0 192.168.25.x/24 Default 192.168.25.1 route to 87.115.17.40/29 via 192.168.25.71 Ping to the machines via tunnel from the VPN Router is working. Now I want to establish a routing from my clients over the VPN gateway and the client packet gets routed to 192.168.25.1 ! traceroute output shows the packets get routed to 192.168.25.71, but then to 192.168.25.1. So the route is not respected in forward ! IPTables and Routing: ip route show 87.115.17.40/29 via 10.45.99.2 dev eth0 10.45.99.0/24 dev eth0 proto kernel scope link src 10.45.99.1 192.168.25.0/24 dev eth0 proto kernel scope link src 192.168.25.71 default via 192.168.25.1 dev eth0 iptables -A INPUT -i eth0:503 -j REJECT iptables -t nat -A POSTROUTING -o eth0:503 -j MASQUERADE iptables -A FORWARD -i eth0:503 -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -s 192.168.25.0/24 -o eth0:503 -j ACCEPT So what is wrong with my setup ? The route is chosen correctly from localhost, but all the clients get forwarded to the Internet GW. thanks for helping, Marcus