Q: AirPort Broadcast Pass Through?

Is your AirPort Extreme base station an 802.11ac model? Is it currently configured with the IGMP Snooping option enabled?

• AirPort Utility > Select the Extreme > Edit > Network tab > Network Options... > Enable IGMP Snooping

What version of iOS is the iPad running? Was is the iOS control program? Was it able to work before or never worked?

You mentioned "Broadcast Pass Through" in the title of your post.

IGMP snooping is the process of listening to Internet Group Management Protocol (IGMP) network traffic. This protocol allows a network switch (for example, built into the Extreme) to listen in on IGMP conversations between hosts and multicast routers. By listening the switch maintains a map of which links need which IP multicast streams. It then learns to forward multicast traffic only to interfaces that require them instead of flooding all the network interfaces.

I was suggesting the you enable IGMP snooping on your Extreme by using the AirPort Utility to do so to see if this helps.

I may not have any, but it would help if I understood a bit more about this "device" you are referring to.

Ah, I'm a HAM myself, just Technician-class in support of my local CERT organization.

Let me do a little research and see what I can find to help you out. Not promising anything, but I'll give it a go.

A broadcast message is not the same as a multicast so my earlier comments really won't apply. Simply a broadcast message will be delivered to every network client regardless of, whether or not, it requests it. In theory, the corresponding application that is running on specific clients will actively listen for this message on UDP port 4992.

One issue can be if the specific client has an active software firewall that is blocking this port. There are actually two types of software firewalls: 1) network, & 2) application. Macs have both, but neither are enabled by default. iOS devices, as far as I know, do not employ software firewalls, so I am a bit puzzled on why you are having issues with your iPad's app.

I'll download an install SmartSDR on my iPad Pro to learn a bit more about it.

Shouldn't the 255 packs from the wired FLEX 6500 just pass through the switch to the wireless side of the Apple AirPort?

Yes, they should. As long as every device is on the same local network subnet, they should pass "through" both the D-Link and the AirPort's built-in Ethernet switches.

If you are familiar with Ethernet switches, you would know that they can operate at both layer 2 & 3 of the OSI model. Devices in the same layer 2 segment do not need routing to reach local peers. They just need to know the destination MAC (hardware) address which is resolved using ARP.

So within this layer 2 environment is where broadcast traffic resides. As mentioned earlier any broadcast traffic going to a switch will be forwarded out all ports with the exception of the port the broadcast packet arrived on. Broadcasts are contained in the same layer 2 segment, as they do not traverse past a layer 3 boundary. In other words broadcasts are limited to their broadcast domain in which they reside. At layer 2 that is an individual network segment. By default, the AirPort uses the 10.0.1.x network segment.

Utilizing VLANs can change all of this. I am assuming that you have not employed this for the simple fact that the AirPort base stations do not support this feature.