DHCP Issue - Apple Devices only

Oh wise CITN network… I am in need of help. We have multiple vlans and multiple ssid’s for our wired/wireless network. The A/V department has it’s own vlan for traffic as well as it’s own ssid on our wireless. The problem that we are having is that Apple devices will not get an address but Android/Windows devices are picking up DHCP just fine. Any idea why Apple would not obtain an address while Android/Windows is more than happy to do so?

I’ve seen problems like this (this was one of the issues I saw on my SonicWALL with SonicPoint implementation that prompted a move to Meraki) and heard about many similar situations on Ubiquity networks.

It almost always comes down to the equipment, in my experience. Spanning tree can be an issue also. Fastest way to knowing where to look first is going to be packet capture and logs. Is the request getting there or being dropped? Is a response being generated at all?

If you’d rather not troubleshoot, I’d check code version of all switches and APs, and look at spanning tree. If that doesn’t fix it, you’re going to have to dig in more to be able to figure out where it’s breaking.

Can you provide more info? Switch models and firmware version, DHCP server information (router or server, how large is the zone, have you checked capacity, etc), AP model(s), etc?

Access Points are Ruckus
Switches are Brocade ICX 7250 (don’t have firmware in front of me at the moment)
DHCP is through our domain controller VM, gives out full addressing on all other ssid/vlan

My apple devices were happy on my aruba network until ios 13. Are the os common?

And the same Apple device will get an IP on a different SSID, no problem?

Correct… it is only their specific vlan that fails. With it set to “DHCP
with manual address” it is able to work proper, on their vlan, as well. It
is just something in that one vlan that is not giving out an address. It
doesn’t matter what access point they are connecting to, we have 20ish, as
long as they try to get on the a/v vlan they will not get an address.

Jeff Eck
IT Coordinator

6100 W. Maple St.

Wichita, KS 67209

316.943.1800, x188

Well, I’m out of ideas then. Anything like channel width stuff would impact all SSIDs on that radio, DHCP helpers/forwarders not working correctly would impact all devices that requested an address.

It sounds like you’re at the stage of doing packet captures and narrowing down to the offending device that way. Maybe someone else has a good idea. Good luck!

It’s actually pretty interesting how Apple devices do DHCP.

Usually, my experience has been that firewalls that don’t use a vanilla DHCPd (a lot use dnsmasq or isc-dhcpd which behave fine) have all sorts of strange issues so if you’re using the DHCPd in the firewall that could be an issue. But with Brocade switches and AD doing DHCP I wouldn’t expect anything untoward. The only thing that comes to mind to me is if you’re filtering broadcasts and arps on that SSID?

I would definitely make sure the core switch is set up with proper DHCP helper address.

I agree that using Wireshark to do packet capture is the best route to see what drops might be happening in the process.

If the helper was configured incorrectly, no devices would get DHCP addresses from that network, right? Unless you know something I don’t, I don’t believe there’s a way around that. And OP mentioned that Android devices work fine on that VLAN.

How about using the DHCP Server on your Brocade ICX 7250 dedicated just for that affected VLAN?

Hello @jeck_81 , Could anyone tell me if this ever got fixed for you? I am having this same issue right now.

If it was me I would create a new VLAN with the same settings (as close as possible) to the one that is not working and try to connect to that VLAN/SSID. If that works just migrate everyone to that VLAN and delete the non functioning one.