ASUS VPN server on FTTP with SmartHub

[pmayberry]

Hi, I have BT FTTP and have recently replaced the Smart Hub with an ASUS router (RTAX58U) to enable me to setup a VPN server (OpenVPN) for use when I am away from the home.  I have also installed ASUS extenders on the wifi network to improve coverage in the house.

The speed of my fibre connection has become variable and, assuming it is not related to the ASUS network, I would like to contact BT to investigate.  This requires me to have the Smart Hub online.

Rather than having to keep switching routers (which will likely result in a new external IP address requiring reconfiguration of the client VPN each time), is it possible to re-insert the Smart Hub between the modem and the ASUS router but still enable the ASUS router to act as a VPN server and my ASUS WiFi to remain operational?  I could then just join the smart hub WiFi from a device, test the speed and engage with BT.

[Crimliar · Accepted solution]

Unless things have changed, you'll only get access to the built-in ASUS VPN abilities when the router is in router mode and not Access Point (AP) mode.  So to sit the RT-AX58u behind the SH2 you'd need to double NAT, which OpenVPN often doesn't like - you may get better results using WireGuard with UDP port 51820 directed to the RT-AX58u.

You might be missing a trick though!  If a part of the issue is not wanting to have to reset the VPN server and clients when because of changing IPs, you should look at using the DDNS ability of the router.

Remember when remotely accessing your home network the connection speeds are asymmetrical, so you'll be relying on the slower upload rate of the router!  Also depending on the hardware version of the RT-AX58u the VPN connection is probably only going to reach 100-150Mbps tops!

[pmayberry]

Thanks for your response Crimilar.  It looks like the DDNS is exactly what I need to solve the problem.  I can now unplug, use the Smart Hub to resolve, and then the VPN will still work when I swap back to the ASUS with a new IP.  Thanks again for your help.

[MarkRocketman]

• Some ASUS routers offer DDNS and ASUS a free service. Sorry I don’t know router so can’t be sure.

[Crimliar]

So far as I'm aware all modern Asus routers have built-in DDNS capability and a dedicated (though a little unreliable) online service it can connect to.  Due to the unreliability of the online Asus DDNS service, I have the built-in DDNS use a Google Domains address.  That DDNS service can be set-up to work in a double NAT environment (one router behind another router - not ideal but sometimes needed) but its more work and only adds to the unreliability.
The built in VPN capabilities of Asus routers allow users to use their router as a VPN server with a variety of protocols or(/and) as a client to many commercial VPN services.  Again this can often work in a double NAT situation but doing so requires more work and is more unreliable!
*Many other third party routers offer the same or similar features!

[TimCurtis]

@Crimliar 

I find the Asus DDNS facility works absolutely perfectly even when my Asus is behind the SH2 - for DV - and will update the IP address for DDNS atleast every 6 hours.

It didn't require me to do anything different to normal when configuring things this way.

[MarkRocketman]

90Million $ Question's ... 

1. Is your Smart Hub 2  in Bridge Mode or using a DMZ  ?

2. Can your Asus VPN find and allow you to connect to your Asus Router reliably through your SH2 ?

3. Is SH2 still capable of providing DV compatability via its green socket ? 

[TimCurtis]

1. DMZ although that's not truly necessary as everything is forwarded to the Asus anyway..

2. DDNS still works and the Asus router app still connects OK when not on local network using the DDNS.

3. Yes

[Crimliar]

Asus DDNS - it depends on what level of reliability you need.  There have been times when their servers have been down for hours which if you are using DDNS to authenticate services has been annoying and problematic!