Error on all Apple Devices: “The name of your computer is already in use on this network”

[m4mazzotti]

Hey there folks,

A few weeks ago I started getting this weird msg on my Mac saying that my computer name was already in use. What I didn't realize at that time is that this was impacting all my Apple devices (Mac, iPhone, iPad and HomePod). I am using a Asus RT-AC68W and a Cisco QOS SG100-16.

After posting that on Reddit, a user mentioned that once he removed his switch, things came back to normal. I felt that was a bit weird (because even my wireless devices are suffering from this), but I decided to give it a try. I powered down my Cisco Switch for a few week to see the outcome. Guess what? Not a single device had to be renamed! (With the Cisco Switch connected to my network, my devices would get renamed on a daily basis).

Any ideas why that is happening and how to solve it? 

[Richard Burts]

We do not know much about the topology of this network and that makes it difficult to give good advice. Can you provide some details about this network? You mention only a Cisco switch. I am guessing that there are probably other switches and perhaps some router(s) in the network. Can you tell us more about them. 

And can you provide details about how the Cisco switch connects to other network devices? I am wondering about the possibility that the Cisco switch connects to some other network device with the Cisco assigning vlan x while the other device has assigned vlan y. If both switches connect to some upstream device it could result in the upstream device seeing you Apple devices as belonging to both vlan x and vlan y leading it to say that the device is already in use.

[m4mazzotti]

Hey Rick, thanks for reaching back!

It is actually a fairly simple home network:

• My ISP Modern is connected is connected to my Asus RT-AC68W via the WAM port
• On my Asus RT-AC68W I am using 2 LAN ports.
  • 1 port is connected to my Synology NAS (DS214play)
  • 1 port is connected to my Cisco Switch
• All other wired devices are connected to my Cisco Switch (I only have 1 switch)
  • Smart TV
  • Desktop PC
  • Sonos Hub
  • Philips Hue Hub

My Asus RT-AC68W is the DHCP server and I am running a guest network (none of the devices above are on the guest network, I only use the guest network for external people). Most of my devices have a Manually Assigned IP (this is done via the Asus RT-AC68W).

Note: I have already double checked on my router and I don't have the same IP assigned to 2 devices.

[Richard Burts]

Thanks for the additional information. There are a couple of things that I would like to clarify:

- Does this error message just pop up at random times? Or is it part of some predictable pattern? Perhaps a reaction to bringing the device onto the network? Or perhaps a reaction to some other type of action or event?

- Is it correct that this error message is generated by Apple devices and displayed on that device? And are the names in the message Apple names and not IP DNS names?

- It seems that the Apple devices impacted by this are all wireless connections. Is that correct? If that is the case I am puzzled that adding the switch which handles only wired connections is impacting devices that are wireless connected.

[m4mazzotti]

Hey Rick,

Most of the times, I feel it happens right after I wake-it-up. However, it did happen a few times while I was browsing the web. I have 5 Apple devices, 4 are wireless and 1 is wired. My Macbook is connected to the network via a ethernet cable (wireless is turned off).

The error is generated by the same device. For instance, if I get that error on my Mac, it is the Mac that gets renamed.

Thanks for engaging on this puzzling journey with me!

[Georg Pauwen]

Hello,

on your Apple devices, under the Energy Saver options, disable 'Wake for network access' and 'Wake for Wi-Fi network access', and check if the issue persists...

[m4mazzotti]

Hey Georg,

That option is not available on iOS (iPad and iPhone). That said, all my devices are being impacted by this weird situation.

Do you still believe it is worth trying?

Thanks!

[Georg Pauwen]

Hello,

if it is related to the wake functionality, I guess iPad and iPhone devices should not be impacted. For the sake of testing, try and disbable it on a Mac, if the behavior changes, at least we know what direction to look at...