I have an IPSec tunnel between my FortiGate (7.0.8 0418) and a SonicWall firewall (version: old).
After much hammering I have it working, but only for clients in part of my network. I'm running using 192.168.8.0/21 as my network and netmask. In my IPSec settings I have this entire range listed as an address group and in my Local Address list. For some reason 192.168.12.1 through 192.168.13.254 can all communicate with the target addresses. 192.168.10.1 through 192.168.10.254 cannot. They are all using the same gateway.
I can get the .10.0 network to communicate if I toggle the "Local Gateway" in the IPSec Tunnel to "ON" and enter my public IP address. This kills the .12.0 and .13.0 tunnel connection. These are both from the same tunnel, running a single Address Group.
The firewall policy is set up so that internal interfaces with the associated internal source can go to the Outgoing interface (tunnel interface) with the destination IP address range. I do see traffic on this policy.
The .10.0 network can communicate with the .12.0 one without issue.
As a note, when I use .10.0 or .12.0 these networks are not subnetted or vlanned out. It is all part of the same IP range (which just adds to my confusion). There are reasons it is the way it is but it is an inherited mess, not a planned one.
Any help would be appreciated. Thank you!