I have a bit of a tricky setup on my Synology NAS:
There is a VPN tunnel up and running which also acts as default gateway (tun0, GW: 10.129.15.229). This is intended and should stay like this so that everything that is initiated on the NAS is going through the VPN.
I now want to use NAT on my local network (initiated by other computers in the private net 192.168.2.0/24, using the local gateway 192.168.2.1).
Just switching on NAT using iptables rules like this
iptables -t nat -A POSTROUTING -s 192.168.2.0/24 -j SNAT --to-source 192.168.2.20
Seems to interfere with the default GW named in 1 (nothing happens/does not work).
Any ideas how I can set this up? Can I mark the packages with iptables somehow and then set up a route to 192.168.2.1 explicitly for those marked packages?