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I hope someone can help me with my setup. I have two WAN routers from different Internet Service Providers. I'll call these ISP_NAT and ISP_PS4 for the sake of this question. ISP_NAT uses NAT444 (CGN) which creates problems during matchmaking in online games, ISP_PS4 doesn't and is perfect for gaming but not as fast ISP_NAT which I use for every other thing.

ISP_NAT (Huawei B5141) is connected to a TP Link Archer C9 router which avails a WLAN network around the house, although the ISP_NAT itself is capable of broadcasting its own WLAN network. ISP_PS4 (Huawei LTE CPE E5172) is connected directly to my PS4 and is the only device using that connection.

The problem is, I have a Plex server hooked up to ISP_NAT which allows client devices on ISP_NAT/TP Link stream videos and whenever I need to connect the PS4's Plex client to the server, I have to switch its connection to ISP_NAT. Considering how often I switch between movies and online gaming, this is becoming a pain. And I'll rather not have the PS4 access the Plex server remotely as that will drive up my internet costs which is very expensive here in Nigeria.

I'm after a solution that will allow ISP_NAT and ISP_PS4 co-exist on the same local network allowing devices access each other regardless of which ISP_* they are connected to.

Is this possible? How can I achieve the desired setup?

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2 Answers 2

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A Better Strategy

(I thought of this a little later; see original answer below)

You can configure your PS4 to use your second Internet connection but still have access to the rest of your network.

Assume your existing network connected to ISP_NAT:

  • Uses the IP subnetwork 192.168.10.0/24
  • The gateway & DNS server is 192.168.10.1
  • The DHCP pool is 192.168.10.100-254

Now:

  1. Assign ISP_PS4's router the IP address 192.168.10.2.
  2. Disable DHCP on the ISP_PS4 router.
  3. Configure the PS4 with a static IP address of 192.168.10.10 and set its gateway and DNS server to 192.168.10.2 (ISP_PS4's router).

Now only PS4 (and only it) will access the Internet through the ISP_PS4 router, but it can communicate with the rest of your network normally.

Original Answer

How to create two networks connected to two ISPs that both need access to a single internal server.

Assume your existing network connected to ISP_NAT uses the IP subnetwork 192.168.10.0/24. Create a second subnetwork connected to ISP_PS4 and assign it to the subnetwork 192.168.20.0/24. In particular:

  1. Assign ISP_PS4's router 192.168.20.1. This will be the subnetwork's default gateway. Configure DNS and DHCP for the network.
  2. Connect your PS4 to the new network.

  3. Add a second network card to your Plex server and assign it an IP on the new network such as 192.168.20.20.

    Note: If your Plex server supports assigning multiple IP addresses on a single network interface you don't need to add a second network card.

  4. Connect the server's second NIC to the second network.

Now your PS4 can access the Internet through ISP_PS4 as well as your Plex server.

Additional Notes

  • If you need your two networks to talk to each other, this can be done, but both routers need to be connected to each other and be configured with a route between them. However, this may require different devices as most residential "routers" aren't true routers because they cannot be connected to more than two networks (i.e. Internet and LAN).

    Note: Should you go this route, you don't need a second network card in the Plex server because traffic can be routed between the networks and therefore your PS4 would have a route to the server.

  • If you need your two networks to share a common cabling infrastructure, this can be done with the following changes and considerations:
    • The second network must have DHCP disabled and use only static IP addresses. Otherwise DHCP (which uses broadcasts) from both networks will compete/conflict with each other
    • Non subnet-specific broadcast traffic (e.g. ARP traffic) will be visible on both networks. In your specific case this shouldn't be a problem, but it's something to be aware of.
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  • Precise instructions, I can't thank you enough. The "better strategy" worked for me :)
    – Ralph
    Commented May 2, 2017 at 14:11
  • Glad it helped. Would you mind if I edited your original question to generalize it a bit so that others might find it more easily and be able to use it for similar situations?
    – I say Reinstate Monica
    Commented May 2, 2017 at 14:12
  • Please go ahead :)
    – Ralph
    Commented May 2, 2017 at 14:15
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A network can only have one gateway.

You could install a real router between the wan routers and your Home network. It could even be a pc with 3 network cards running linux.

In that router you would set rules for which devices connect over which WAN interface when making outbound connections. The devices would be able to communicate between each other on the local network.

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  • Those gateways are real routers, though their configurability is somewhat poor. If one of them ran OpenWRT or something such...
    – grawity_u1686
    Commented Apr 30, 2017 at 23:18
  • I would disagree only because of the terminology issue. DDWRT cannot create hardware functionality where none exists. Consumer devices are really a media Gateway(bridge), a firewall, and a switch in an Unholy Trinity. I know technically that's a perform routing functions however they only perform them between 1 WAN connection and the internal switch. They don't have the ability to set even QOS rules. Even with DDWRT installed you are unable to reuse switch ports for additional wan or dmz uses. You need a real router for these types of functions.
    – Rowan Hawkins
    Commented Apr 30, 2017 at 23:41
  • Linux with more than one network interface can provide all of the real router functionality needed by the OP. None of the devices they currently have can support the needed functionality.
    – Rowan Hawkins
    Commented Apr 30, 2017 at 23:48
  • Thank you for your answer, I was able to do this by following Twisty's instructions. All I had to do was: 1. Assign a static IP in the same subnet as my main router. 2. Disable DHCP. 3. Connect ISP_PS4 (Secondary connection) to Archer C9 (Home Router). 4. Update PS4's network to use the secondary connection's IP as gateway.
    – Ralph
    Commented May 2, 2017 at 14:14
  • 1
    The solution the OP employed in my answer does not create two networks. Instead it allows a single network to be served by more than one gateway, and simply has devices that wish to use the second network use the alternate gateway. While multiple gateways is unusual, using them is not contrary to proper network design. In fact, most DHCP servers are capable of assigning multiple gateways to DHCP clients.
    – I say Reinstate Monica
    Commented May 4, 2017 at 1:55

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