IPv4 and v6 through different ISPs?

Installing and Using OpenWrt
1

Hi,

I am facing the following challenge:

  • Fibre-ISP is providing IPv6 only (IPv4 NAT) (1/0,5 GBit down/up)
  • (backup-)WWAN-ISP is providing IPv4 only (two options - either a) both IPv6 and IPv4 NAT OR b) public dynamic IPv4 with no IPv6 at all; I choose b) to be able to access my network from abroad) with unlimited 5G-max (300/50 Mbit down/up)
  • I am hosting some publicly available services that I setup for IPv6
  • In some rare cases when fibre is down I want my services to be available as well

My first idea (A) was to have all IPv4 traffic routed at anytime via WWAN and all IPv6 traffic routed via fibre connection. But that would limit outgoing IPv4- connections always to 300 MBit which is not acceptable.

Next idea (B) is to

  • (B.1) have all outgoing traffic routed via fibre and in case of rare fibre connection losses (which in those cases can last for days, so I really need some backup solution) switch outgoing traffic to WWAN.
  • (B.2) at the same time route all incoming IPv4 traffic to my services at any time via WWAN. If the connection was down there is no backup as fibre would not be reachable via IPv4 anyways.

(B.1) could be covered by mwan3, right?

Could (B.2) be covered with PBR?

Best and thanks (at least for reading),

ssdnvv

2

Yes

Yes again, you can use PBR e.g. the full PBR-app or do it manually OpenWRT Policy Based Routing (PBR)

But why not use your IPv6 address to connect from outside?

Or use something like Netbird or Tailscale to connect then you do not need a public ip address

3

Ok, thanks. I will come back for detailed questions that arise during setup.

I do.
But there are circumstances (like company networks), where IPv6-services are even in 2026 not accessible.

So this would enhance accessibility of my services.

4

Regarding VPN - as one part of my services is a webserver hosting one Nextcloud and one dokuwiki instance I share with family and friends, netbird or alike services would not be a solution in my case.

But there's one other central thing I forgot to ask above: if I setup my webserver to be accessible both via IPv4 and IPv6 - is there via PBR a configuration option to prefer IPv6 over IPv4 for incoming connections (as stated above the IPv6 upload speed is ten times the upload speed of IPv4)?

5

Assuming your webservices runs on a server in your lan and not on the router, it might work to use the IPv4 IP address of the server to route back via the IPv4 interface.

Never tried it so not sure.