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Intermittent Connection Drops with Xfinity

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Regular Visitor

Intermittent Connection Drops with Xfinity

I have Comcast Xfinity in the San Francisco Bay Area. I've been experiencing intermittent connectivity drops for several months, and have finally gotten around this weekend to investigating a little more deeply. The equipment I'm using is listed below.

 

Modem: Arris Surfboard SB6141

WiFi Router: Netgear WNDR3700v2

 

I always use wifi at home, never the wired connection directly into the modem. The behavior I see is that I'll be working online, everything is chugging along just fine, and then the connection drops for ~1-5 seconds and then reconnects. When I'm working from home, I have a VPN client open, so I can see in real-time when the connection drops and when it re-connects because the client will show me a pop-up message when the connectivity changes. During this time, websites are unreachable.

 

This morning I had a couple of terminals open and I was pinging google.com and my wifi router to try to see if the culprit is the signal from the router, or upstream of the router. I think the evidence shows that it's not the router. Here's what I saw during one such instance of connectivity loss this morning.

MacBook-Pro:~ user$ ping -t 100 google.com
PING google.com (216.58.194.174): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
92 bytes from 73.158.249.244: Destination Host Unreachable
Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst
 4  5  00 5400 08c1   0 0000  3f  01 1554 192.168.2.3  216.58.194.174 
Request timeout for icmp_seq 2
Request timeout for icmp_seq 3
Request timeout for icmp_seq 4
Request timeout for icmp_seq 5

Meanwhile my router was returning pings the whole time.

MacBook-Pro:~ user$ ping -t 100 192.168.2.1
PING 192.168.2.1 (192.168.2.1): 56 data bytes
64 bytes from 192.168.2.1: icmp_seq=0 ttl=64 time=0.990 ms
64 bytes from 192.168.2.1: icmp_seq=1 ttl=64 time=1.204 ms
64 bytes from 192.168.2.1: icmp_seq=2 ttl=64 time=30.186 ms
64 bytes from 192.168.2.1: icmp_seq=3 ttl=64 time=1.741 ms
64 bytes from 192.168.2.1: icmp_seq=4 ttl=64 time=2.641 ms
64 bytes from 192.168.2.1: icmp_seq=5 ttl=64 time=1.126 ms
64 bytes from 192.168.2.1: icmp_seq=6 ttl=64 time=2.516 ms
64 bytes from 192.168.2.1: icmp_seq=7 ttl=64 time=5.234 ms
64 bytes from 192.168.2.1: icmp_seq=8 ttl=64 time=3.084 ms

 

I've pasted below some data from my modem from http://192.168.100.1. 

 

DOCSIS Downstream Channel Acquisition Done
DOCSIS Ranging Done
Establish IP Connectivity using DHCP Done
Establish Time Of Day Done
Transfer Operational Parameters through TFTP Done
Register Connection Done
Cable Modem Status Operational
Initialize Baseline Privacy Done

 

DOWNSTREAM

Channel ID 40  41  42  43  44  45  46  47 
Frequency 627000000 Hz  633000000 Hz  639000000 Hz  645000000 Hz  651000000 Hz  657000000 Hz  663000000 Hz  669000000 Hz 
Signal to Noise Ratio 38 dB  39 dB  39 dB  38 dB  39 dB  39 dB  39 dB  39 dB 
Downstream Modulation QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256 
Power Level 4 dBmV   4 dBmV   4 dBmV   4 dBmV   4 dBmV   4 dBmV   4 dBmV   4 dBmV  

 

UPSTREAM

Channel ID
Frequency 36700000 Hz  30300000 Hz  23700000 Hz  17300000 Hz 
Ranging Service ID 12616  12616  12616  12616 
Symbol Rate 5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec 
Power Level 44 dBmV  45 dBmV  45 dBmV  45 dBmV 
Upstream Modulation [2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
Ranging Status Success  Success  Success  Success 

 

 

Channel ID 40  41  42  43  44  45  46  47 
Total Unerrored Codewords 59942129  58666486  58674658  58657397  58647740  58648935  58645702  58650305 
Total Correctable Codewords 11  23  37  63  151  115  14 
Total Uncorrectable Codewords 1472  1459  1464  1435  1493  1402  1419  1494 

 

Does anyone have a recommendation about how to proceed? I'm not entirely sure where to go from here.

 

 

EDIT

 

It occurred again about 15 minutes after I made this post while I was poking around the forum. I had a terminal open - this time I was pinging google.com, 192.168.2.1, and 192.168.100.1. The connectivity dropped for about 10 seconds. During that time, pings to both google.com and 192.168.100.1 timed out. Pings to 192.168.2.1 were returned as usual. Checking my modem logs, I see the following.

 

Feb 09 2020 08:45:17 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=20:3d:66:09:f2:f3;CMTS-MAC=00:01:5c:62:ac:4a;CM-QOS=1.1;CM-VER=3.0;
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Expert

Re: Intermittent Connection Drops with Xfinity

The signal stats were o/k at that snapshot in time. For a test, does a computer hardwired directly to the WNDR3700v2 router with an ethernet cable have the same problem ?

 

As a second test, does a computer hardwired directly to the 6141 cable modem have the same problem ?



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Regular Visitor

Re: Intermittent Connection Drops with Xfinity

Yes, I can confirm that this still happens when I am wired directly into my router, and when I am directly wired into my modem.

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Regular Visitor

Re: Intermittent Connection Drops with Xfinity

Can anyone from Comcast please respond to this? I'm seeing frequent T3 timeouts multiple times per day.

 

Here's a modem log from June 15: https://pastebin.com/x0CknJk3.

 

And here's a modem log from June 14: https://pastebin.com/At9kkXtL

 

 

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Regular Visitor

Re: Intermittent Connection Drops with Xfinity

Would love some attention from Comcast here.

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New Poster

Re: Intermittent Connection Drops with Xfinity

Same issue here.

When the wheather is hot, it will frequently reports T3 timeout error in the modem, and disconnect the Internet access.