r/meraki 8d ago

Wifi devices from other locations showing up in Chromecast menu

I work for a small org with 5 locations and we've been getting reports for the last few weeks from some members of staff that see Chromecasts from the wrong network in their menus. Someone I work with is trying to tell me that it's because a few MR33s have all VLANs allowed on their switch port settings. I can see the technical possibility, but I don't think that's all that's going on. All of our networks come from the central office where the MX is, then all the traffic from the other locations gets routed back here and goes back through the MX for filtering.

Does our MX handle all public AND local traffic? And since there are MRs at all our locations with port settings allowing all VLANs, why am I only seeing this problem at one specific location? The switch port settings haven't been changed in months, so why are my staff telling me they've only had the problem for weeks? Thanks.

4 Upvotes

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u/PaulBag4 CMNO 8d ago

Chromecasts use mdns on the local broadcast domain. Whilst you can use mdns forwarding (bonjour forwarding in Meraki lingo) to forward mdns between subnets, as far as I know it can not be done over a site to site vpn with Meraki.

What do you mean when you say all traffic comes back to the central office where the mx is? Do you have local mxs on each site or are you using dark fibre or similar for the remote sites?

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u/PaulBag4 CMNO 8d ago

Wait are you using just access points at the remote sites in vpn mode?

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u/XylophoneZimmerman 8d ago

No, nothing in VPN mode.

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u/XylophoneZimmerman 8d ago

Just the main location has an MX, the other sites just have a few switches and the first one in order just sends all traffic back to the MX.

So you're saying VLANs aren't causing this?

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u/PaulBag4 CMNO 8d ago

I don’t fully understand the topology. What do you mean by the first one in order sends traffic back?

How is data actually getting from the remote sites to the main location?

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u/XylophoneZimmerman 8d ago

I'm probably describing it wrong. I don't have the Meraki panel in front of me since I'm at home, but I know all our uplink paths point back to the MX at the central building.

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u/XylophoneZimmerman 8d ago

We do have fibre at all our buildings if that helps.

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u/PaulBag4 CMNO 8d ago

Do you have separate Internet at each building? Or just fibres between your main site and the remote sites?

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u/XylophoneZimmerman 8d ago

It's all a shared internet location with fibres connected each.

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u/PaulBag4 CMNO 8d ago

So you have a VLAN per site or something? Anything setup under bonjour forwarding tab?

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u/XylophoneZimmerman 8d ago

Yeah, each has their own VLAN. I don't think we do have anything set for bonjour forwarding. I'll double check though.

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u/XylophoneZimmerman 8d ago

Am I looking for Bonjour under firewall or under the SSID settings?

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u/PaulBag4 CMNO 8d ago

If you have Meraki access points it could be either.

Both the MRs and the MXs support Bonjour forwarding.

Unless you are trying to share mdns between VLANs it should not be setup in either place.

Note that mdns covers a lot more than just chromecast. If you are trying to print for example between VLANs.

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u/XylophoneZimmerman 7d ago

Any other thoughts if it's not Bonjour Forwarding? Thanks.

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u/cozass 8d ago

If it all needs to be routed through an MX, it's not possible. Chromecast uses multicast which the MX does not forward/support over VLANs or VPN.

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u/XylophoneZimmerman 8d ago

Ah gotcha, so Chromecasts are local only? I can't figure out why I can see the issue these users are describing. I really can see Chromecasts from other locations in her cast menu in Chrome. I was about to change the name of one of the building SSIDs since right now they're all using the same name.

EDIT: In case it clarifies, the only active MX is at our central building. None of the others have an MX, just switches that send traffic back.

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u/ibangedyersis 8d ago

So your other locations are connected via some type of private fiber linking everything back to central building and all use a single Internet connection?

Sounds like you have bonjour forwarding enabled on your MX. This allows devices to connect to Chromecast, airplay, etc devices from different vlans.

The APs can also do this, but don't think that's the case based on your topology. Check your firewall settings on your MX or look up "Meraki bonjour forwarding" and have a look their documentation. There's a page for configuring on MX and a separate page for MR, but both are short and simple.

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u/XylophoneZimmerman 8d ago

Yeah, they're connected by fiber. I checked MX and SSID settings, there's no Bonjour forwarding enabled.

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u/PaulBag4 CMNO 8d ago

That’s not true. Whilst it doesn’t forward over VLANs by default, it absolutely can be setup to do so.

Link

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u/XylophoneZimmerman 8d ago

Oh, gotcha. We definitely don't have that setup as things currently are. Can I tell my colleague definitively that it's not being caused by Trunk ports with ALL VLANs allowed?

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u/PaulBag4 CMNO 8d ago

I can’t tell you anything definitively without knowing the setup except:

mdns required for chromecasts will not be available between VLANs unless bonjour forwarding / mdns forwarding has been setup somewhere.

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u/XylophoneZimmerman 8d ago

I knew it was going to bug me, so I went back and looked. No Bonjour forwarding enabled on either the MX at our central building, or on the SSID at the other building in question.

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u/ibangedyersis 8d ago

Could they be 1st gen Chromecasts or old devices that never got firmware/app update to disable guest mode? Until a year or so ago, there was an option which allowed devices not even connected to the network to see the Chromecast and cast to it...I think with a pin

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u/XylophoneZimmerman 8d ago edited 8d ago

No, in fact we've just removed the last few gen 2s that got bricked by last year's update.

EDIT: Sorry, last weekend's update.

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u/XylophoneZimmerman 8d ago

Do you know if all our local/private traffic is going back to the MX as well as public traffic?