Asus OpenVPN tunnel - Server LAN cannot access client Asus Router Gui.

[NotTom]

Hi,
I currently have a 3 nodes (1 server and 2 clients) site-to-site openvpn tunnel setup between 3 asus RT-AX58U. The tunnel is working fine and every nodes can reach the LAN of the other 2 nodes. However for some unknown reason that I can't figure out, the server node cannot connect to the GUI interface of the 2 others ASUS routers (and only the asus routers).

In a nut shell:
Client 1 : Router - 192.168.1.1 (LAN 192.168.1.0/24)
- Can successfuly connect to a NAS on both Client 2 LAN & Server A LAN.
- Can successfuly connect to ASUS router on both Client 2 LAN & Server A LAN.
Client 2 : Router - 192.168.2.1 (LAN 192.168.2.0/24)
- Can successfuly connect to a NAS on both Client 1 LAN & Server A LAN.
- Can successfuly connect to ASUS router on both Client 1 LAN & Server A LAN.
Server A : Router - 192.168.3.1 (LAN 192.168.3.0/24)
- Can successfuly connect to a NAS on both Client 1 LAN & Client 2 LAN.
- CANNOT connect to ASUS router on both Client 1 LAN & Client 2 LAN.
- Can reach the GUI page of a second asus router setup in Aimesh on client 1, but the redirection from Aimesh router to the main router 1 just timesout.

I'm wondering if I'm missing some tunnel instruction or if this a limitation built in the Asus routers. While I have no proof, it feels like the 2 client routers are droping requests to themself, when it originates from the LAN of the server through the openvpn tunnel.

Has anyone experienced the same issue with Asus routers ?

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tunnel opions:
- Local network only (activated)
- TUN
- UDP
- Push LAN to client (activated)
- Allow client <-> client (activated)
- Allow only specific client (activated)
- 2 clients are added with their LAN/Subnet + PUSH (activated)
- (no custom configuration)
- tunnel set up to use 10.8.0.0/24