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How do I tell if it's Comcast, or my gateway router, causing random internet disconnects?

  • 2 January 2023
  • 3 replies
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In the last several months I’ve had to power down/power up my “Xfinity-compatible” SBG6900-AC Gateway Router dozens of times because one or more of our computers or iPhones mysterious lose Internet connection. How does a Comcast Xfinity customer figure out whether it’s a problem with my SBG6900, or some kind of problem with Comcast Xfinity?   My SBG6900 error log shows repeated Critical arcane events like, “ No Ranging Response received - T3 time-out” and “ Started Unicast Maintenance Ranging - No Response received - T3 time-out” or “Honoring MDD; IP provisioning mode = IPv6, No Maintenance broadcasts for ranging opportunities received - T2 tiime-out”. It’s all but impossible to talk to a human Xfinity technician anymore; all phone support leads me in circles. The cynic in me also wonders if Comcast is trying to drive customers to exasperation who bought their own gateway routers, to get them to rent Xfinity’s equipment again, due to “growing incompatibility” or some such pretext.

 

NOTE: there was no selectable CATEGORY for my SBG6900-AC so I selected a near equivalent.

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plemans
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t3 errors tend to be line issues. 

Do you have a screen snip of the cable connections page and the event logs? 

 

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this.

 

Current setup: Netgear CM3000-->Netgear RBE973S-->2.5gig tp-link switch, Xfinity 1.4gig/240mbps
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Thanks, plemans, for the tip on T3 errors...You may be onto something! Our neighborhood’s buried Comcast main cable feed runs in a line behind everyone’s houses, emerging up inside periodically spaced junction towers where the main coax is tapped and individual branches are re-buried and fed to  small hinged Comcast boxes typically mounted 4-5 feet up on people’s outside walls. Hurricane Ian submerged Comcast’s main cable towers throughout our neighborhood, to a depth of at least 12 inches, for 3-4 hours. As a first step, I’m going to get a Comcast tech out here to inspect and signal-test our feed line; it’s quite possible there’s some water or condensate in those coax connections that could be causing the T3 errors.  I’ll update this thread when I find out what they discover.   Again, many thanks for explaining about T3 errors.

plemans
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Good luck! Comcast it notorious for putting things off or saying “its not our line”

Current setup: Netgear CM3000-->Netgear RBE973S-->2.5gig tp-link switch, Xfinity 1.4gig/240mbps
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