Access Modem and Asus Merlin router via VPN

[lionkd75]

I use the internet provider's modem/router only as a modem. I have connected the Asus Merlin router AC2900 (WAN port) to the LAN port of the modem. pppoe passthrough is activated in the modem, so the Asus router makes a second connection (pppoe). Everything works great and when I connect to Asus' wifi I can access the modem in 192.168.1.1 and the Asus router in 192.168.10.1 (I have changed the LAN address of the Asus). So far so good. Now, the VPN server is running on the Asus, and when I am using 4g and VPN I can access the Asus in 192.168.10.1 but not the modem in 192.168.1.1. Is there any solution in order to access both via VPN?

 

[SoFluffy]

Other than I may not know/understand potential caveats of pppoe passthrough, one of my setups is Asus (192.168.10.1) behind a combo router/modem (192.168.0.1), so a double NAT. When ovpn’d in to the Asus, I can hit both subnets without doing anything special. I do have the OpenVPN settings to route all internet traffic, so is routing all subnets other than the local client‘s subnet via OpenVPN gateway. If that is not your desired behavior, internet search “push route” entry and add that with your desired subnet/mask/metric to your OpenVPN config, and that may solve your issue.

Another side issue I had was when the client’s local subnet was also 192.168.0.0/24, but that is easily explained and should not likely be the case with your 4G connection.

 

[drinkingbird]

I use the internet provider's modem/router only as a modem. I have connected the Asus Merlin router AC2900 (WAN port) to the LAN port of the modem. pppoe passthrough is activated in the modem, so the Asus router makes a second connection (pppoe). Everything works great and when I connect to Asus' wifi I can access the modem in 192.168.1.1 and the Asus router in 192.168.10.1 (I have changed the LAN address of the Asus). So far so good. Now, the VPN server is running on the Asus, and when I am using 4g and VPN I can access the Asus in 192.168.10.1 but not the modem in 192.168.1.1. Is there any solution in order to access both via VPN?

So when you're connected to the VPN, you're coming from somewhere remote to access your home LAN? Are you sure that remote place doesn't have 192.168.1.x as their IPs? If so your traffic may not even be hitting the VPN.

If that isn't the case, try a traceroute to 192.168.1.1 and see if it makes it to the Asus or is getting blackholed somewhere. It may just be a matter of adding a route somewhere, but since 192.168.1.x is so common, I'm thinking something is conflicting.

 

[lionkd75]

Thank you both for your answers
I am using 4g remotely so I guess there is no conflict with 192.168.1.x.

I am also using another VPN server in a NAS which is connected to the Asus. In this case, I can reach both the modem and the Asus in 192.168.1.1 and 192.168.10.1 respectively. So it seems it is something going on with the Asus and not with the modem, otherwise it would not work with the NAS' VPN server as well.

@SoFluffy is it something I need to ad in the openVPN client config or in the Asus VPN server config? It seems to be a route issue or maybe a firewall issue in the Asus?