Comcast XFINITY → [Connectivity] Upstream Power Levels (out of spec) with IP Change?

I've got an Arris TG862G/CT gateway with performance 25/5 plan. Actual speed 30/6 with no connection problems. I've been on Comcast for 2 months and haven't disconnected my DSL ( the wife needs a reliable connection for work) and have been monitoring the gateway connection stats periodically for stability before I give ATT the boot. About a week ago my modem got a software change/upgrade indicated in the event log (it took a power cycle to regain the full gateway web interface capability) and an ip change from 24.98.25.xxx to 76.97.243.xxx. Along with it the upstream power levels went from a constant 51.0 to as high as 54.75 dBmV. That is outside the recommended range and the TG862G/CT spec of 54.0. There have been no changes to my cable tv wiring or extreme weather along the way only ip address and gateway software.

Is it possible that the Comcast network change caused my high upstream power levels? Since I'm an admitted cable rookie, any suggestions on how to proceed are appreciated.

You probably should call for a tech visit. Not only is your upstream dBmV too high, your downstream levels are too low. The downstream should be between -10 to +10 dBvM.

As cHarley said, both your upstream and downstream are way out of specs: »Comcast High Speed Internet FAQ »What should my Signal Levels be?

Before you call for a tech visit, though, you may want to check your home cabling for any issues.

How is your modem connected to your line? If your line also feeds any set-top boxes for TV sets, then your line should first feed a 2-way splitter, with the line to your modem connected to one port, and the other port then feeding the line going to the set-top boxes, which may be further fed from other separate splitter(s).

Otherwise, the poor levels could be due to the use of a poor-quality splitter, bad or poor cables (RG-6 is recommended, quad-shielded RG-6QS is preferred), excess cable lengths, or bad fittings/connections.

If all those are not the case, then go ahead and request a tech visit to troubleshoot your levels.

Your IP may have changed but you didn't change CMTS's or anything like that I checked..Not on the IP side.. Like everyone is saying I would check splitters and cables..

A look at my wiring to the modem I find a 4 way splitter and a 2 way splitter in the way of the signal. Just bypassing the 2way I get stats like above. Much improved. Looks like I need to take telcodad's advice and split the signal between modem and 3 TVs at the outside box.

Does anybody make an unbalanced 4 way splitter with a single port at 50%?

Yes, that's better, but the upstream signal levels are still a bit high, leaving little margin for any variation on the upside. If you can reduce the loss by another 3 dB that would be good, like you indicated next in your post:I've never seen such a 4-way splitter myself.

What you'll have to do is first have the signals go through a (good quality) 2-way splitter, and have one port feeding your cable modem and the other port feeding a (good quality) 3-way splitter for the TVs.

Most 3-way splitters are the "unbalanced" type, where one port is marked like "-3.5dB" (50%) and the other two "-7dB" (25%). In that case, if you have a long run of cable to one of your TVs, you can put that one on the "-3.5dB" port to help compensate for the greater cable loss.
 
EDIT: I don't know what the quality of that 2-way splitter that you have is, or what shape it may be in (as your downstream levels jumped by about 8 dB instead of about 4 as would be expected by removing it), but here are some high quality 2- and 3-way splitters I can recommend:

2-way:
»www.amazon.com/Splitter- ··· 08R3LOM0
»www.amazon.com/Sv-2g-2-w ··· 03TH36CK
»www.amazon.com/EXTREME-D ··· 07YV0UQW

3-way:
»www.amazon.com/Splitter- ··· 0I82D6OY
»www.amazon.com/Unbalance ··· 0HFU4MTS
»www.amazon.com/Extreme-U ··· 09FMHHX2