Redirecting traffic to IPSec tunnel

Hi,
we have working IPSec tunnel from our network 192.168.23.0 to IBM Cloud network 192.168.24.0. Each of this network is behind firewall with public IP. Our firewall is Linux IPFire. IBM side is Cisco. Connection between those local networks works fine.
We have also OpenVPN clients notebooks connecting to our local network with IP 10.8.0.0. They can access our local network.
What we are missing is connection between OpenVPN clients and IBM network 192.168.24.0.
Also, we have to access internet from IBM through our firewall (through IPSec). Default getaway of IBM network 192.168.24.0 is 192.168.24.253, which direct all packages to IPSec tunnel.
IPfire web interface does not allow this connections and it is quite a task to go through the rules generated by this web interface. I decided to reinstall firewall and use SLES 11.
Can somebody point me in right direction regarding forwarding packets to IPSec tunnel? Do I have to use pre-rutting SNAT, so that packages not originating in 192.168.23.0 have changed source IP to firewall’s IP 192.168.23.253?
Thanks for help.

See this is your first post here: welcome.

That having said, reading your post I can nowhere find any connection with openSUSE (that is what our forums are about).

There seems to be a lot of general network knowledge involved and you mention SLES somewhere.
Now it is quite possible that someone here finds your thread and has some suggestions for you, but you may be better served at the SLES/SLED forums:
SUSE PRODUCT DISCUSSION FORUMS