GS110TPv3 incompatible with Ubiquiti Unifi UAP-AC-M

Hi everyone, 

I'm faced with an issue between the devices GS110TPv3 and Unifi UAP-AC-M.
On the UAP-AC-M I have two SSIDs:

• MAIN -> This SSID is using untagged network communication
• SECOND -> This SSID is using VLAN-ID 100

The UAP-AC-M is powered by the switch.

The untagged network uses default "VLAN" 1. The GS110TP is connected to an GS750E where also the DHCP Server (Unifi USG) is connected to.

UAP-AC-M <-> GS110TP <-> GS750E <-> USG

When I connect to the MAIN SSID, the Client doesn't get an IP from DHCP (stuck while obtaining IP). Also when I set static IP to the Client, I don't have any Network access! This is my issue.

But when I connect via SECOND SSID, I will get an IP from DHCP and can connect to the network without any issues.

I have checked a hundred times that the Ports are well configured (VLAN 1 is untagged, VLAN 100 is tagged from end-to-end).

When I wireshark the Port where the UAP-AC-M is connected, I see that the broadcast for DHCP request is coming from the device - but will never get an response.

When I wireshark the Port which is connected to the GS750E, I see that there will never receive the DHCP-broadcasts!

But I see also, that this communication when connecting to the SECOND, tagged SSID will go through both interfaces!

Because also with static IP I will have no network access via MAIN SSID, also other untagged traffic is not managed by the switch.

I don't know why packets are getting "lost" within the switch. I disabled all advanced features like DHCP snooping etc. So it should be a stupid switch with VLAN.

Do you have any idea. I am working on this issue since days and come to an dead-end.

Just to be sure - I have tested several UAP-AC-M and the issue looks like the same on every device! When I connect the UAP-AC-M directly to the GS750E (with PoE injector because of missing PoE in this switch) everything works well without any issues!

Thanks for your help. Hopefully we will get a solution because if this is a really incompatibility I don't know how to get official support.

Best,

Harry