Disable Intranet access for a LAN port (not the WiFi Guest network)?

[Rici]

Hi,

Since I have an OpenWRT router ready to be configured for handling all my IoT devices, so that I can keep them separated e.g. via VLANs as well:

How to restrict Intranet access to the other LAN & WiFi clients on my Asus RT-AX86U Pro router running Merlin 3004.388.8_2, when I connect the OpenWRT router to one of the Asus' LAN Ports (such as Port 2 or 3)?

Do static routes help, such as: Everything coming from LAN port 2 always only goes to the WAN port (and therefore to the Internet), but cannot be spread across the LAN & WiFi clients of my Asus router?

Of course, VLAN would also be an option. Unfortunately, Merlin still does not have implemented that yet for the AX-86U Pro, despite Asus supporting it (including Guest Mode Pro for IoT devices). Or have I missed something here from Merlin and VLAN support?

 

[eibgrad]

If you have a separate OpenWRT (or even DD-WRT, FreshTomato, or Merlin) router, you don't need to do anything on the primary router AT ALL! Just connect the WAN of the secondary router to a LAN port on the primary router. By definition, the LAN behind that secondary router *is* another VLAN! All you have to do is make sure it's using a different IP network from the primary router, and add firewall rules to limit access from that secondary IP network to the internet and NOT the immediate upstream network.

 

[Rici]

Thank you!

Regarding "add firewall rules to limit access from that secondary IP network to the internet and NOT the immediate upstream network": What exactly do I have to do to ensure that?

 

[eibgrad]

Unfortunately, my experience is primarily w/ Merlin, FT, and DD-WRT.

With Merlin (or ASUS OEM), all you really need is to use the NSF (Network Services Filter).

The following DD-WRT example is typical.

ddwrt-guest-router-firewall.sh - Pastebin.com

Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time.

pastebin.com

It specifically blocks access to the immediate upstream network, and ANY other private networks. It also limits access of the secondary router itself to only essential service (typically DHCP and DNS, although if you configure public DNS servers for your devices, you don't even need that). Finally, I provide an example of an exception, such as access to an upstream printer.

FT would be very similar (perhaps identical) to DD-WRT.

I believe OpenWRT requires a more text-based means to configure the same rules.

 

[Justinh]

@eibgrad thank you for sharing those details. After doing a shell configuration of the FW, would any of it show in the GUI in the appropriate places?

 

[Tech9]

@Justinh, you can do this on your RT-AX86U Pro in GUI. It's part of the new Guest Network Pro function, you can assign a port to VLAN.

 

[bennor]

To go along with what Tech9 indicated. See the LAN port mode in the following Asus article.

[Wireless Router] What is VLAN and how to setup in ASUS Wireless Router? | Official Support | ASUS Global

 

[Justinh]

@Justinh, you can do this on your RT-AX86U Pro in GUI. It's part of the new Guest Network Pro function, you can assign a port to VLAN.

Right. Just want to learn about this method.

 

[Tech9]

The method above is a workaround with two devices when this functionality is not available on the main router. It is available on your router, at the moment in stock Asuswrt only. As per your signature you are running stock Asuswrt. Look at the link @bennor provided above.