Enable Overlap IP Address in a FortiGate VDOM

Here's a Fortinet link to enable an overlap IP address in a FortiGate VDOM. I've subnetted a public IP address range and allocated a /31 subnet for the point-to-point WAN link to an ISP.  I wasn't able to configure the /31 public IP address since it had a subnet overlap in another interface.

FGT (interface) # edit "npu0_vlink0.10"
new entry 'npu0_vlink0.10' added
 
FGT (npu0_vlink0.10) # set vdom "isp"
 
FGT (npu0_vlink0.10) # set ip 46.40.14.8 255.255.255.254
Subnets overlap between 'npu0_vlink0.10' with primary IP of 'po1.10'
node_check_object fail! for ip 46.40.14.8 255.255.255.254
 
value parse error before '255.255.255.254'
Command fail. Return code -54

I had to configure the set allow-subnet-overlap enable command under the VDOM setting and I was able to apply the /31 public WAN IP address afterwards.

FGT # config vdom

FGT(vdom) # edit isp
current vf=isp:4
 
FGT(isp) # config system setting
 
FGT(settings) # set allow
allow-linkdown-path     Enable/disable link down path.
allow-subnet-overlap    Enable/disable allowing interface subnets to use overlapping IP addresses.
 
FGT(settings) # set allow-subnet-overlap
enable     Enable overlapping subnets.
disable    Disable overlapping subnets.

FGT(settings) # set allow-subnet-overlap enable

FGT(settings) # end