Greeting all, 

I am posting this both to see if anyone else has run into this issue, and also to offer up the solution I came up with in case wnyone else expereinces a similar issue.  I had a very strange issue come up in the last day. 

FIrst off, I am using the M9 Plus as noted, in conjuncton with a Linksys E5600 router.  The router IP address I use is 198.162.1.1 - this will be important later.  The E5600 router has all wi-fi functions disabled, and the M9 mesh is set up in access point mode only.  I have all 3 of my M9 units connected via wired ethernet for backhaul. I've had this configuration in place for about 6 months without issue up to this point.

Last night my entire network was working fine, except I had a brief period where the wi-fi seemed to be unavailbale for a few minutes (phones switched over to LTE) and then started to work again, while all my wired connections (i.e. Amazon firestick streaming) were working.  Today, I woke up to find that all of the Windows based PC's I have, which are all wired ethernet connections, were having issues with internet connectivity.   In an effort to resolve the issue, I did a few PC restarts, and then also restarted the router.  Ultimately, after seeing that the issue was present on all the Windows PC's I had running on the local netowrk, I ran "IPconfig" at the Windows command prompt and found that the default gateway that the PC's were pointing to were set to 198.162.1.122. This caught me by surprise, as I had expected that the default gateway should have matched the router address. When I punched in this IP address into my web browser, much to my surprise, the TP link internet interface came up (I had actually never used the web interface - only the smartphone app up to this point).  I checked on both the web based interface and in the smartphone app, and they both indicated that the M9's were all in access point mode as they should have been, but for some reason, the PC's were apparently trying to route throught the primary M9 instead of the E5600 router.  Doing a reboot on the primary M9 caused it to release the IP address, and then all the PC's updated their default gateway to the correct router address, and all was back to normal.  What was very odd in all of this is that most other wired devices, (streaming firesticks, Sony PS5, etc.) seemd to work fine through all of this, it was only the wired PC's that had an issue.  Also, all the wi-fi devices seemed to be unaffected, and two separate work laptop PC's running via wired etherenet, but connected to their respective company VPN's were also unaffected.  It seems as though somehow, the local windows based machines (both Windows 10 and Windows 7 - don't ask why I'm still using a W7 machine), were getting the wrong connection, such that they could not access the internet, BUT they were able to see other networked devices (i.e a NAS storage system).  So the ultimate fix was very easy, but diagnosing the problem was tricky at best (at least for me). 

Again, I am sharing this in case anyone runs into a similar issue - and just to see if anyone else has seen this happen, or has any thoughts on how this could have happened in order to prevent a recurrance.  To me, this looks to be more of a Windows issue than ann M9 issue, but I can't help but feel that somehow the M9 was doing something it should have been for the PC's to look to it as a router in the first place.

Thanks!