Yeah, you are essentially correct Brecht. I'll make an attempt to explain this in my own words for anyone that needs clarification: Depending on the mDNS-device (Apple-TV, Chromecast, etc, i will use all these names varyingly depending on what i feel best explains what i mean) the usual way it works is that the mDNS-device multicasts it's capabilities on the broadcastdomain/VLAN (TTL1) with a service-string (ex: _googlecast._tcp.local.). If you are lucky (or very knowledgeable before buying the devices) it is a generally accepted service-string that is the same no matter which device you plug in. If you are unlucky it is a device-unique service-string (_9967AQ0s243._sub._googlecast._tcp.local.), the "lucky" part will be explained below. Now, i haven't actually seen this config on Meraki and can't really tell you about that, but since its "Cisco" it should be similar to other Cisco WLCs (Cisco has made their WLCs into mDNS-proxies): -first you need to make a mDNS-profile; Cisco Provides a default with the most common services but that default might not include all the service-strings your mDNS-devices broadcasts. Either read the documentation on the mDNS-device and add any mentioned service-strings, or sniff the chromecast-VLAN for all mDNS-broadcasts and make a list of offered service-strings. The Standard Chromecast servicestring is "_googlecast._tcp.local." or "_chromecast._tcp.local." but it depending on vendor (my experience it's usually the "Smartboard"-vendors that does this) it might be "VendorArbitrarilyChosenUniqueIDForThisSpecificDevice._tcp.local" (this basically means you need to add exactly every devices specific string intead of just "_googlecast._tcp.local"). -you then activate mDNS (bonjour IGMP sniffing) on the WLAN Profile and specify what profiles to use for sniffing service-strings ("the one you made" or "default"). -you then go to one of the APs on the site where you have the Chromecasts and want to provide this mDNS-device service and configure it to sniff in a specified VLAN (klick the AP, go to "advanced", mark "mDNS-snooping" and then specify what VLANs the mDNS-devices are in) -go to the switch that this AP is connected to and make the switchport into a trunk with both the management-VLAN and the mDNS-Device-VLAN. -Now the accesspoint can sniff for the services on the mDNS-VLAN and populate a global list of available services in the WLC. -when a wireless device now wants to use these services it will make a mDNS-query on wifi and depending on how the controller is configured the controller will provide the client with the list (default it will send the whole list which might include services on other sites which isn't really a favorable thing). -to limit the list of devices that the controller returns to querying clients you need to make a mDNS-policy in WLC and fill that list with the source MAC-addresses of the Chromecast-devices and then apply that list to either a specific AP (meaning only clients connected to that specific AP will get the list) or to an AP-group (meaning if the client is connected to an AP in the AP-group it ill get the list). that covers the signaling part of mDNS. -now the client knows of the available mDNS-services on the network, it will now try to contact the device for use. Depending on the mDNS-device this will be either by Unicast or by Multicast. This is in my experience usually default Unicast-SSL which is why i upvoted BrechtSchamp 🙂 (For the specific services of Chromecast/Apple-TV/Airprint/AirPlay, etc, it doesn't make sense to make the streaming part of the device into Multicast, if the mDNS-device was a camera or a monitoring tool with several client-monitors showing the same thing it would make more sense to use Multicast for the streaming part) -Unicast method means that the client will be routed through the network to the chromecast and everything should work as peer-to-peer communication (i.e. if it is the same vrf, you are already done configuring). If you have a firewall separating the "office network" from the "Chromecast network" you need to make sure that the client is allowed to contact the Chromecast through the firewall (chromecast uses ports usually ranging UDP/32768-61000 and TCP/8008-8009). For Apple-TV or other mDNS-devices it might be other ports and you need to sniff the traffic or google the used ports for that specific mDNS-device. -if it uses multicast traffic for transporting streaming/data you will first need to make sure that your network supports Multicast routing and then also make sure that the traffic is allowed through any firewalls that separates the networks. I hope this helps clarify for anyone new to mDNS. /Mike
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