Devices connected to router can't reach devices connected to access point when using the same SSID?

Question

I seached and tried different solutions for hours but can not get this to work. Hopefully someone is able to help me.

The Setup:

Main router (Salt Fiber Box) with IP 192.168.1.1 It has 2.4ghz and 5ghz wifi activated. Automatically assigned ip-adresses are configured to be between 192.168.1.100 - 192.168.1.200 using the latest firmware: v.1.01.26 build83

Access point (Asus RP-AC68U) is connected via LAN (LAN to LAN) and has a static IP assigned (192.168.1.2). It runs in AP-Mode and also has 2.4ghz and 5ghz wifi activated. DHCP is turned off. using the latest firmware: v.3.0.0.4.382.40019

Security settings are the same on both devices. AP-Isolation is deactivated on both devices. If I use the same SSID and password for all 4 wireless signals I can successfully connect and depending on the signal strength it also switches to the best signal.

EDIT: 29.01.2021 - 11:03, added images of configuration

https://imgur.com/a/rK0jgrR (using placeholder for SSID and KEY)

The Issue:

If I am connected to the main-router's wifi with my phone or notebook I am not able to ping for example my philips hue bridge which is connected to the access point. I installed the wifiman app on my smartphone and it is able to find and list all the devices correctly even I if I am connected to the main router. But all devices connected to the access point are listet with 100% packet loss.

As soon as I walk over to the access point and my device switches the signal and I can successfully reach all devices attached to it.

The strange thing:

If I use different SSIDs (SSID_1 for the main routers 2.4ghz and 5ghz signals and SSID_2 for the access point 2.4ghz and 5ghz signals) it works. I can take my phone, connect to the SSID_1 of the main router and successfully reach the devices connected to SSID_2.

The Summary

As I told I already searched for hours and tried different settings. But it just wont't work. The only things I always read are "make sure DHCP is turned off for the access point", "make sure the same security settings are used", "make sure to use a static IP for the access point", "Do not use the WAN port". But I already considered all these things. In my eyes the setup is correct. I just don't understand why it works when I use two different SSID names and as soon as I use the same SSID for all signals the devices become unpingable.

I also tried to turn off firewall settings without success and I lately assigned static IPs to all my important devices to have a better overview of what exactly is connected to which endpoint. Also if a new device connects to the access point the ip assignment is done fast and correct within the specified range on the main router and all devices have a stable connection to the internet.

Is there anyone who already experienced simmilar issues or has any idea what may be configured wrong?

Answer 1

If I use different SSIDs (SSID_1 for the main routers 2.4ghz and 5ghz signals and SSID_2 for the access point 2.4ghz and 5ghz signals) it works.

That's because WLAN uses a three-address schema to allow bridged APs with a wired backbone. And this doesn't work with different IP ranges.

So if you want the same SSID for the Main Router and the Access Point router, you need to bridge both APs to LAN. Consumer router firmware often makes this difficult or impossible; open firmware like OpenWRT can help if it supports your hardware (but even then there's no friendly UI to set this up correctly).

This also means you'll have a single LAN segment with a single address range (consider something bigger than /24 if you have many devices) in both your LAN and WLAN, and you also should only run the DHCP server on one router.

If you have no idea what all of the above means, it may be simpler to just keep using different SSIDs.

Answer 2

Well my ap is an old apple extreme that still has good firmware and wireless specs. I have a mesh system. Modem wired to wan port on main router. Main router wirelessly connects to second router. This mesh is my DHCP provider. My apple extreme is an access point at my apple Computer. Mesh Router is wired to the WAN port on AP. Then computer is wired to LAN on AP. DHCP is disabled on AP. But if I disconnect it’s WAN connection from the mesh router I lose internet to my LAN connected computer and any wireless devices near by the AP. The AP becomes just a client with no ability to reach host internet. The only thing I see out of the ordinary in my network is my daughters apple laptop is a wired connection to the router when it isn’t, but this normal because the router is wired to the modem so the router is assuming this device (but not all my connected devices?) is etherneted to the Internet. But the laptop ALSO has a wireless connection to the AP with the same IP address as the Ethernet connection on the main router. If there was a DHCP conflict then the laptop would have two different ip addresses. But only my main router is DHCP enabled. The two different connections with the same IP is what’s a little bit puzzling to me but isn’t causing a problem on my network or any connectivity issues with the laptop. Essentially it’s trying to say one network card, one IP address, two different connections to two different AP’s. But I think you need to connect the router via Ethernet cable to your ap. Make sure the dhcp is off on the ap. Then connect any devices you want etherneted locally to ap to ap’s lan ports. Your router that’s acting as your dhcp provider can also be connecting devices on any open lan ports as well. In case u didn’t already know that…