raspian stretch as ethernet router to VPN not routing between interfaces

Question

I am trying to replace an old box with Rpi to simply provide a VPN connection to some remote point from my LAN

All the parts seem to work. From the Rpi I can ping etc local and remote devices and vice versa.

However I can't get a connection between devices on my LAN and the remote LAN.

The firewall is off. The Rpi just has a single Ethernet connector and has two ethernet interfaces - one the ethernet interface and the tunnel interface.

Routes define which interface to use to access the local and remote LAN addresses.

It is as though the Rpi/Stretch doesn't know how route between the two interfaces.

There is no special configuration that I know of in the old Redhat box I am replacing or the other end of the VPN on a Busybox based switch, they just have disabled firewalls and appropriate static routes defined.

Any advice welcome Thankyou

Answer 1

If everything works as expected, except the packet forwarding, then you should verify that packet forwarding is enabled.

You can see the current state with

sysctl net.ipv4.ip_forward

You can enable packet forwarding with

sysctl net.ipv4.ip_forward=1

You can make the setting permanent by placing it in a file in one of the directories mentioned in man sysctl.