Routing Internet Traffic via Windows computer Without Changing Default Gateway

[AlcMat]

Hello, just for purpose testing, in case of internet provider outage, I want to route all local network internet traffic through a Windows 11 machine that is connected to the local network via Ethernet and to a mobile hotspot via Wi-Fi, while keeping the pfSense firewall as the default gateway for all network devices.

Network Scenario

• pfSense firewall (LAN interface): 10.0.0.1 (default gateway for all devices)
• Windows 11 machine (Ethernet - LAN): 10.0.0.10 (static IP)
• Windows 11 machine (Wi-Fi - Hotspot): 192.168.137.2 (automatically assigned by mobile phone)

Goal

My objective is to allow all devices on the 10.0.0.0/24 network to access the internet through the Windows 11 machine's Wi-Fi connection, without requiring any changes to their default gateway (which must remain 10.0.0.1).

What I Have Tried So Far

I have attempted the following approach, but not have worked successfully:

1. Enabling IP Forwarding on Windows (IPEnableRouter in the registry) and turned off windows firewall
2. Adding Windows (10.0.0.10) as main gateway on pfSense

Maybe a NAT problem?

Any guidance would be greatly appreciated. Thank you in advance for your help!

[viragomann]

@AlcMat said in Routing Internet Traffic via Windows computer Without Changing Default Gateway:

Enabling IP Forwarding on Windows (IPEnableRouter in the registry) and turned off windows firewall
Adding Windows (10.0.0.10) as main gateway on pfSense

Maybe a NAT problem?

You have also to masquerade the traffic with an outbound NAT rule to avoid asymmetric routing.

Enable the hybrid mode in the outbound NAT.
Add a rule:
interface: LAN
source: LAN net
destination: any
translation; interface address (LAN address)

You can also configure a gateway group on pfSense to do the failover automatically.

[AlcMat]

@viragomann I have this outbound rule but I get stuck here:

tracert 9.9.9.9:

1    <1 ms    <1 ms    <1 ms  firewall.pfsense [10.0.0.1]
2    <1 ms     *        *     Computer.with.hotspot.wifi [10.0.0.10]
3     *        *        *     Request timed out.

[viragomann]

@AlcMat
Sniff the traffic to see if the masquerading rule works properly.

If it's fine that's all you can do on pfSense. Then there might be something wrong on the Windows machine.