Not sure why the possibility of a duplicate IP address is so ludicrous to you. But in any case, my thoughts go much more towards potential wifi interference first. 

But I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR. And we, the public, don’t have access to it. 

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Routers/firewalls use DHCP.  The odds of a DHCP service handing out two IP’s when they are all tracked in the DHCP table is extremely unlikely.  So unless you setup your network with static IP’s in the same range as your DHCP scope, this is essentially impossible.

Anyway, contacting support seems to be a lost cause as well based on what I have been reading.  So I am looking here to see if anyone has actually resolved the issue as it seems to be fairly common.

Thanks!

My personal experience has been that a DHCP table, on some routers, perhaps that have been ‘attacked’ by things like a power surge, have lost their ‘place’ in the DHCP table.  Subsequently they have handed out duplicate IPs in error. due to the fact that Sonos devices, which request ‘new’ IP addresses each time they update their firmware. This is something that happens more frequently than most other devices, as well as the fact that streaming music tends to expose periodic interruptions more easily than most other devices. 

Usually, a reboot of the router resets both the firmware, and its memory of the DHCP table’s allocation process, and a reboot of the Sonos devices forces them to reload their own firmware, and request new IPs from the refreshed router. I’ve run in to this type of situation myself, with a Netgear router, while living in Texas, with the occasional power surges caused by atypical thunderstorms. I’m delighted that your system is immune to such a possibility. 

I do hope that someone stops by and gives you ann answer you are willing to accept, and hopefully is correct as well. 
 

Edited: cleaned up ridiculous run on sentence, and slightly modified for clarity. 

It is alway best to try things yourself instead of relying on what you read elsewhere…..

Thanks for the help.  I have tried a lot of things.  Resetting my internet router, resetting the firewall to factory, resetting my wireless AP’s to factory, resetting my switches to factory, resetting these speakers to factory.  There are no network issues, only the flakey experience of Sonos.  So I have tried a lot of things and the only common denominator are these speakers.

i also replaced my my firewall to rule it out.

So I came here to see what others have said and so far it doesn’t seem that anyone has resolved this issue.

I would add, I never had a problem with the Sonos One, play bar or the older sub.  I got all new Sonos products and now none of it works properly. 

Ok, here is what I just completed.

I unplugged all the speakers and factory reset them one at a time, reconnecting them to my wireless network.  I was then able to create the home theatre and everything so far is working.

I am not sure what the difference is or what changed, but this last attempt to reset all the speakers seems to have worked.

I will update this in a couple days to let people know if it’s working.

In Summary:

Factory reset the following devices:

• Firewall
• switches
• AP’s
• Swapped out FW
• All Sonos products

After all this, I reset each speaker and re-added them.  They were no longer even showing up in the app.

Once I re-added each speaker, I was able to add the Sub and the two era300’s into a surround system with the arc ultra.

This could have been any of the above devices at this point, but having reset and reconfigured all devices it seems to work.