Considering that this thread is regarding the MI424WR and its usage as a MoCA bridge, I thought I would share my success story.
I initially purchased a pair of ECB2200 (HME2200) MoCA adapters from Amazon a while back. My mom's house is devoid of ethernet networking and I am unable to install it. Wireless is not a great option since it is a large ranch house. Phoneline networking is poor because of interference with the power lines in the house. I am sure the power lines in the house are too old to give me a good connection by PowerLine. So I went with MoCA. I just plugged in the two ECB2200's at the two locations I wanted them, the coax light went on and I had a 100mbps connection between the two locations.
(One thing I want to point out is that initially I had the cable modem running off the coax-out port of one of the ECB2200's. I figured that since the downstream was around 29.4 MHz and the upstream was around 717 MHz, as indicated by the config page, and MoCA was stated to operate above 1 GHz that there wouldn't be a problem. I found that there was a problem and the cable modem would consistently lose connectivity. I even tried a splitter, having the ECB2200 on one output and the modem on the other, to no avail. The upstream SNR was not terrible, but it seemed the MoCA was interfering in some way, which is why I just moved the cable modem to its own dedicated line as you can see in the attached diagram of my setup.)
I didn't want to pay $70 more for another ECB2200 so after researching on the internet, reading that the MI424WR would interact with the ECB2200 I decided I would get an MI424WR router to try. I got one off of Craigslist for $20, a Revision E (Rev E) model.
I first read the directions on setting this up as a bridge. That is, I followed the directions in the first post here: http://www.avsforum.com/avs-vb/showthread.php?t=1145636
However, because I also wanted the router to be a wireless access point, I skipped step 4 and left the wireless enabled, and in step 8 I checked the boxes next to the Wireless connection.
After I had the router all set, I plugged it into the Coax line, but nothing happened. The coax light did not go on, but the ECB2200's were running fine. I then tried moving the MI424WR next to one of the ECB2200's, running it off the coax-out port from the ECB2200. That also did nothing. I finally decided that I should try unplugging everything and repowering everything. With the MI424WR hooked to the ECB2200 coax-out port, and the coax-in port still hooked to the cable line, I powered everything up and every unit worked perfectly - all three units lit up with their coax light. It seems that the router needs to dictate to the ECB2200's what frequency to use. I unplugged the MI424WR and put it in the location I wanted it, plugged it back in and it still worked great.
I attached a picture of the setup I have:
Yellow triangle = Comcast-supplied amplifier
Purple Circle = Comcast-supplied cable modem
Solid Blue Circle = television with no STB
Blue circle with red diamond = television with DTA STB from Comcast
Blue circle with cyan diamond = television with HD STB from Comcast
Blue circle with black diamond = tv tuner in a computer
Green Circle = ECB2200
Red Circle = MI424WR router connected by coax
Gray box = 1000 MHz Comcast-supplied splitter
Orange box = 900 Mhz unshielded splitter I picked up from the hardware store
I get the full 100mbps connection with this setup (or well, 94mbps as I saw in the bandwidth meter). The MI424WR log says the connection supports 224mbps down, 226mbps up.
One of the ECB2200 units is connected to a router, with DHCP enabled, that is connected to the cable modem. A computer is connected off of this router.
The other ECB2200 unit is directly connected to a router setup as a wireless/ethernet bridge with DHCP disabled (similar to the MI424WR settings). A computer is connected by ethernet to this router.
A computer and a sumsung TV are connected to the MI424WR by ethernet, and I can connect wirelessly to it.
Everything receives an IP without issue.
For those interested, the MI424WR recognizes the computer and the samsung tv connected to it (by ethernet) as ethernet connections, anything connected wirelessly as wireless connections, and everything else is identified as a coax connection.