WeMo and Home LAN

Note: I have replaced all my WeMo switches. I don't recommend using them. But, I had them for more than 3 years. So, some of my WeMo work might help others.

This issue started back up again, and there is no rogue AP. I gave up on WeMo and replaced by 31 Smart switches with another vendor

I have figured out a root cause of WeMos dropping off my network. 

• When expanding my home LAN, I added two switches and two Wi-Fi Access Points in a daisy chain configuration. In effect, devices connecting to each were on their own network segment. I direct connected all four to the gateway and the first level of issues went away.

• I inadvertently added a "rogue" DHCP server to my network. I was playing around with a Raspberry Pi project and so I did it. It really wasn't rogue. And I did it intentionally as an experiment, but thought I had shut it down. Once I shut down the DHCP Server, all of the other issues went away.

My WeMos ran fine for quite a while. But then something changed and the WeMos started dropping off the network at a very high rate (~3/week).  And then it would settled down, and no more would drop off.

The order seemed to be: 

• I'd lose control of the WeMo from Amazon Alexa, 

• I'd lose control of device from WeMo app, and then 

• the WeMo doesn't appear on the gateway.'s status page

However, after running various tests and watching it over time, it seems the devices were becoming dysfunctional in the opposite order

In the past, a few WeMos might drop out if the ISPs gateway rebooted, or if I updated the software.

I am constantly adding to and changing my network. So, I thought it was something I did. And, it was!

My gateway is an AT&T GigaPower, Arris BGW210-700.

• The 2.4GHz band on the BGW210-799 is limited to 80 devices

• However, the practical limit seems to be 16-20

• If the limit is exceeded, then after a while devices will drop off the network. There is not data to support these conclusions. I have 17 or 18 Wi-Fi devices on each 802.11n AP

• It is not unusual for an AP to advertise a "high" limit on maximum simultaneous devices, but have a much lower practical limit 

I read WeMos should have a fixed IP address to prevent drop out. So, I tried setting static IPs. However, this doesn't work for me on the BGW210-700 because:

• The BGW210-700 static IP allocation table only allows 20 static IPs and I have almost twice that installed

• There is no way to remove a static IP without factory resetting the BGW210-700

• When I would change a WeMo from DHCP to static, then it would change from a wemo device to unknown

My original network was daisy chained as shown below. All of the WeMos connected to one AP on my ISP's gateway. 

All the devices are bridged. So, there is only one IP Address range 192/168.1.0/24. The gateway limits the last octet of DHCP to 64-255

All of the APs, including the gateway, have two radios and can broadcast on both 2.4GHz and 5GHz simultaneously.

I started working on this issue in earnest while trying to write a bash script that would return the IP address, MAC Address and hostname of each WeMo device. But, regardless of what I ran, the results were inconsistent. 

I ran the commands and scripts and commands from my MacBook connected to one of the 802.11AC APS.

Each program or script would give very different results. I would get somewhere between 10 to 20 WeMo devices out of the actual 29 WeMos installed.

nmap and arp weren't providing comprehensive results. So, I knew something was wrong. I thought my MacBook might be aggressively removing arp table entries. It wasn't!

On the configuration below, 

• I disabled both radios on the gateway

• Each standalone AP has two radios. One is for 2.4GHz and the other is 5GHz. I am using four unique SSIDs.

• 802.11b/g are disabled and the 2.4 GHz radio only supports 802.11n, which is what WeMo supports. 

  • Belkin recommends 802.11n with bandwidth set to auto 

  • 802.11n has a range of 175 feet indoors, so should be adequate for most houses

• The 5GHz radio is 802.11ac only and is not used by WeMo devices.

The WeMos and other N-only devices are split evenly between the two N-only SSIDs (~18 each).

When trying to google a solution, someone recommended setting the BGW210-700 in pass through mode. However, DON'T do this. In pass through mode, the BGW210-700 moves the public IP from the AT&T Gateway to one of my switches or APs

Troubleshooting WeMo Network issues

Power-Cycling seems to fix most issues.

• Power-cycle the gateway and wait 5-10 minutes

• And then power-cycle each of the other APs and switches, waiting 5-10 minutes before doing the next one

In the top configuration, if I ran nmap or arp I'd only get 35-50 devices of the ~80 installed on my home LAN, and only 10-20 of the WeMos. This command, run from my MacBookon Wi-Fi, is more consistent, yielding 26-29 WeMos consistently out of 29 installed

• sudo arp-scan -t 10000 --interface=en0 192.168.1.0/24

This WeMo utility is great:

• python3 wemosetup.py discover

Sometimes the above doesn't work, or Alexa is unable to discover all WeMo devices

• Disable the WeMo skill in the Alexa app

• Re-enable the WeMo skill and re-link it