Troubleshooting and Diagnosing MoCA Network (ScreenBeam Devices)

[cam0001]

Hello,

I recently installed 3 pairs of of the ScreenBeam MoCA adapters (5 adapters installed + 1 spare), configured Network Privacy, ip addresses through DHCP on the same LAN as the network I wanted to extend. They have been working fine overall l without major issues.

However, today, out of the blue, one of the adapters (the one that is connected to the network switch that provides access to most of the devices I want to connect) stopped working (The coax cable light turned off). (The other 4 adapters had both LEDs on).

First I thought, something was wrong with the coax cable this adapter was using (which I had replaced today as well). However, after getting a different cable, and power cycling the adapter, I couldn’t get it to work and connect to the other ones (coax cable light to light up).

I then started power cycling the rest of the adapters (one at a time). At first, each adapter wouldn’t join back to the Network (coax light off) after I turned it off and back on, until I power cycled one of the adapters (which happened to be the last one to power cycle), and then all of them started working right away.

This made me come up with the following questions:

- What made this happen? (I am concerned because if this happens again, everything will stop working until I manually power cycle all of them, not reliable).

- How can I prevent this from happening again?

- Is there a good wat to monitor or troubleshoot issues?

- Do these adapters have a CLI?

Thanks.

 

[degrub]

1) moca modems do not need an ip address on your lan. They are transparent to your lan. Reset them to factory. Enable security if you want. A moca POE filter at the top of your moca network should work just as well.

2) do you have power blips occasionally? A ups can be beneficial.

3) there could be a failing power brick on one of the modems. More likely than a modem failing and a devil to prove.

4) are there any other devices on your coax that use moca ( DVR perhaps) or do you share the moca coax with a DOCCIS 3.1 modem ?

 

[cam0001]

Thanks for the reply.

1) I can reset them, but I'd like to make their IPs part of my LAN just for convenience to access their web interfaces to check their status and performance. I do have the Moca filter installed a well (between the coax cable coming from outside and the main splitter).

2) Not really. The adapter I mentioned that was having issues, is actually protected by a UPS.

3) good point. I have a spare moca Adapter with its power supply. I might with to swap them to test.

4) Yes. The Moca Adapter that has issues is actually sharing a coaxial cable with a DOCSIS 3.1 Modem (Motorola MB8600). The coax from the wall connects to a 2-way splitter where one goes to the Moca Adapter and the other one to a DOCSIS 3.1 Modem. (not my preferred setup, but I don't seem to have another way to get this connected).

As per the document below, the cable modem operates in the 108-1002 Mhz frequencies..

https://en-us.support.motorola.com/...edirect/1/filename/MB8600-DataSheet-28317.pdf



Can that be a problem?

 

[degrub]

No, that is DOCCIS 3 territory and not a conflict..
power, overheating, would be my bet , either wall warts or the device, since they ran well for a long time.

 

[unioncorps]

3 things to consider, though you may already have done these:

1. Is the 2-way splitter you're using rated for MoCA? (i.e., 5-1675 Mhz or is it the standard 5-1002 Mhz?)
2. Are your modem downstream and upstream power levels within spec? Asking because if your downstream or upstream power levels have been "living on the edge" at the max tolerance ranges, your modem can do weird things like reboots and disconnections and all it takes is temperature differences/moisture or other environmental influences that can push it over the threshold.
3. You mentioned changing out the coax from the MoCA adapter that was having issues that goes to the splitter. What about the coax from the wall to the "IN" port of the splitter?

 

[cam0001]

Thanks for your reply... Yesterday I made the following changes:

1.- Changed the splitter for one rated for MoCA (5-1675 Mhz). Before, I was using the standard 5-1002 Mhz. This change made sense once I thought about it. (However, if the previous splitter was only rated for 5-1002 Mhz, wouldn't this make MoCA not even connect to the other nodes?).

2.- Moved the MoCA adapter away from between a switch and a patch panel where it was sitting to about 2ft away. Before I made changes in the last 2-3 days, the adapter was 2ft away from any of these other networking devices so I thought some kind of interference could be playing a role here (How much are these coax signals prone to interference?).

Things have been stable since I made these changes (Not sure if it was #1 or #2 or a combination of both) that is making it work better. I'll keep my fingers crossed. If it works solid for the next 24 hours, I think I can make some conclusions..

I've attached the list of the Phy Rates as seen today. Node "0" is the one where I have been having issues. If you notice, there's few nodes that are connecting at a lower rate (<2500), with a couple under 2000. Is there a way to troubleshoot this? All adapters are 2.5 so I'd aim at getting all rates between devices in the > 3000 range.

 

[unioncorps]

For #1, I think using a standard 5-1002 Mhz splitter will still work but it'll be at the expense of throughput/speed I believe (i.e., sub-optimal).

For #2, I'm actually referring to looking into your cable modem signal. Like logging into the admin page to view signal stats for downstream and upstream power levels to ensure they are within spec. Also, in that admin page, you should be able to see if you're getting modem errors in its log. If the signals are out of spec, you can expect some connectivity issues or the modem outright rebooting.

 

[degrub]

1) some splitters do not have a sharp cutoff at the edge of the band. So, as mentioned above, they may allow enough signal for moca to sort of work.
2) if the coax shield, terminations, and connections are as they should r connectionsbe, then, no.

The link rate table tells you that the signal path between both 0 and 1 to #4 is degraded somewhat such that they are only using 3 of the 5 possible moca 2.5 bands. I would investigate that path for poor connections, whiskers in the connectors, other splitters, kinked coax, etc. it may help you if you sketch out a layout map with all the coax and devices and connections shown.

 

[cam0001]

Something I just realized is that the 5-way splitter installed by the ISP at the demarc, is rated for 5-1002 MHz . This can be contributing to the lack of performance (even though it still works).

I‘ll get a MoCA splitter to replace it.

 

[degrub]

Is it in the moca path ?
i thought you had a moca poe filter at the 2 way moca splitter in the house ?

 

[cam0001]

Below is the diagram:

Red boxes are Moca adapters (issues with #0 is what started this thread) ..

Shouldn't the 5-way splitter be replaced by one covering 5-1675 Mhz? (As I understand, all Moca traffic still goes through that splitter)

 

[unioncorps]

Yes, your 5-way splitter should also be 5-1675 Mhz to accommodate MoCA signals.

Random question - is your cable modem a combo of modem and router?

 

[krkaufman]

Shouldn't the 5-way splitter be replaced by one covering 5-1675 Mhz?

Most definitely should be a “designed for MoCA 2.x” splitter, with the 1 GHz splitter potentially contributing to lower PHY rates. But you might consider an alternative, using 2 splitters in place of the pictured 5(?)-way splitter: an initial 2-way splitter (w/ “PoE” MoCA filter on its input port) to feed the modem location and a secondary 4-way splitter, to minimize losses at the cable modem.

Also, as a precaution, you may consider adding an additional MoCA filter directly on the DOCSIS 3.1 modem’s coax port, to prevent any possible interference.


edit: p.s. I’m interested in the brand & model # of the existing top-level 5-way splitter. A 5-output splitter is usually the realm of powered amplifiers, not a passive splitter. A non-MoCA amplifier would definitely contribute to poor MoCA connectivity, especially if the modem and main MoCA adapter are connected to the passive output port, placing them on the opposite side of he amp circuitry from the other 4 amplified outputs.

 

[degrub]

If you use a 5 port passive splitter, make sure the coax going to the two way splitter attached to the cable modem is connected to the port with the lowest loss number. For example, some of the ports may be labeled as “11dB “ and one may be labeled as “7 dB”. The latter s the one you want to use. This minimizes the signal strength loss between the demarc and the modem. Otherwise, you would have to use an amplified moca2 splitter with either zero loss or positive gain to ensure enough signal strength to the modem.

if everything is in one place ( modem, router, 5 port , 2port splitter) i would put the 2 port with moca poe on inlet at the top connected to the coax from the demarc. Then the modem goes on one branch and your replacement moca 2 passive splitter on the other branch. Best layout to avoid signal strength issues.

 

[cam0001]

Most definitely should be a “designed for MoCA 2.x” splitter, with the 1 GHz splitter potentially contributing to lower PHY rates. But you might consider an alternative, using 2 splitters in place of the pictured 5(?)-way splitter: an initial 2-way splitter (w/ “PoE” MoCA filter on its input port) to feed the modem location and a secondary 4-way splitter, to minimize losses at the cable modem.

Also, as a precaution, you may consider adding an additional MoCA filter directly on the DOCSIS 3.1 modem’s coax port, to prevent any possible interference.


edit: p.s. I’m interested in the brand & model # of the existing top-level 5-way splitter. A 5-output splitter is usually the realm of powered amplifiers, not a passive splitter. A non-MoCA amplifier would definitely contribute to poor MoCA connectivity, especially if the modem and main MoCA adapter are connected to the passive output port, placing them on the opposite side of he amp circuitry from the other 4 amplified outputs.

I checked the splitter, and instead of a 5-way splitter, there's actually 2x 4-way splitter (CommScope SV-4G) daisy chained. I bought 2 splitters today through Amazon (Amphenol MoCA 2.5 3-way and 4-way) to replace the old ones.

 

[cam0001]

If you use a 5 port passive splitter, make sure the coax going to the two way splitter attached to the cable modem is connected to the port with the lowest loss number. For example, some of the ports may be labeled as “11dB “ and one may be labeled as “7 dB”. The latter s the one you want to use. This minimizes the signal strength loss between the demarc and the modem. Otherwise, you would have to use an amplified moca2 splitter with either zero loss or positive gain to ensure enough signal strength to the modem.

if everything is in one place ( modem, router, 5 port , 2port splitter) i would put the 2 port with moca poe on inlet at the top connected to the coax from the demarc. Then the modem goes on one branch and your replacement moca 2 passive splitter on the other branch. Best layout to avoid signal strength issues.

That's what I'll do. However, instead of the 2 port splitter, I'll use a 3 port one (This one has an outlet with -3.5dB signal, which I'll use to connect the cable modem to).

 

[degrub]

Usually, the system will have lower losses if you use a single splitter rather then cascading splitters. All of the insertion loss numbers for each connection in the signal path add up. Moca modems usually don’t have an issue. The ISP coax modem can be vulnerable which is why you want to keep the path losses as small as possible.

any open ports on the splitters must be terminated wth 75 ohm caps. Amazon has those too.

 

[cam0001]

Usually, the system will have lower losses if you use a single splitter rather then cascading splitters. All of the insertion loss numbers for each connection in the signal path add up. Moca modems usually don’t have an issue. The ISP coax modem can be vulnerable which is why you want to keep the path losses as small as possible.

any open ports on the splitters must be terminated wth 75 ohm caps. Amazon has those too.

I wish I could put a larger splitter there, but I don't have the room. all this was crammed up in a 2-gang outlet box in the wall when this unit was built. The next Moca Adapter I saw online, was 8-ports, and won't fit there. Great call about the 75 ohm caps (In this case all ports will be used).

 

[krkaufman]

That's what I'll do. However, instead of the 2 port splitter, I'll use a 3 port one (This one has an outlet with -3.5dB signal, which I'll use to connect the cable modem to).

Just as good, at least for the modem line. It’ll add some unnecessary loss for the runs off the secondary splitter if you only need the 5 coax lines. Whatever port goes unused should be capped with a 75-ohm terminator.

 

[krkaufman]

I wish I could put a larger splitter there, but I don't have the room. all this was crammed up in a 2-gang outlet box in the wall when this unit was built. The next Moca Adapter I saw online, was 8-ports, and won't fit there.

Take a look at Amphenol’s hybrid MoCA splitter,

• Amazon product link

(In this case all ports will be used).

What’s changing relative to your diagram. Which shows only 5 coax lines?