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XB10 on 2 Gbps symmetrical: upload dropped from 2 Gbps to 13–670 Mbps and intermittent outages since Oct 9
Since Friday, Oct 9, 2026 (around 6:30 PM PT), my connection has intermittent outages and upload has collapsed. Download is still normal. My plan is 2 Gbps symmetrical, with an
XB10 (CGM601TCOM, software 8.6p4s4) in bridge mode
Upload history (daily automated test from my router at 3:34 AM):
- Sep 2 – Oct 9: ~1.9–2.2 Gbps upload every day
- Oct 10: 130 Mbps
- Oct 11: 2.6 Mbps
- Oct 11 5:27 PM, speedtest.xfinity.com: 1,814 down / 406 up
- Oct 13 (computer connected directly to the gateway): 13–19 Mbps shortly after a reboot, then ~670 Mbps a few minutes later
Outages:
- Starting Oct 9, 6:31 PM; more than 30 on Oct 10, typically 2–5 minutes each
- Oct 11, 7:00–7:06 PM: for the first minute the gateway itself still responded instantly (0% loss to 10.0.0.1) while the internet was unreachable; DHCP renew/discover went
unanswered for ~5 minutes. The Ethernet link stayed up throughout.
- I removed my router and connected a computer directly to the gateway. The drops still happen: ~1 in 3 pings lost during episodes, with latency rising from 10–15 ms to 30–63 ms.
Gateway status page:
- High-band upstream OFDMA channels won't stay locked: ch 50 (105 MHz), 51 (200 MHz) and 52 (297 MHz) were all Not Locked for ~2 days.
- After a reboot, ch 50 and 51 locked, but upload was only 13–19 Mbps. About 7 minutes later ch 51 dropped again and upload recovered to ~670 Mbps. Ch 52 hasn't come back.
- ATDMA ch 1–4 and OFDMA ch 41 stay locked. Upstream power is moderate (ATDMA 37–38 dBmV, OFDMA 29–37 dBmV).
- Downstream SC-QAM is clean (SNR 47–48 dB, +5 to +6 dBmV, 0 uncorrectables).
- Downstream OFDM ch 194 (1086 MHz) is at -11.1 to -11.8 dBmV, and about half of its codewords need correction (0 uncorrectable).
- The gateway event log shows no DOCSIS events, so I can't see T3/T4 or partial-service history from my side.
|
Upstream |
Channel Bonding Value |
|||||||
|
Channel ID |
1 |
2 |
3 |
4 |
41 |
50 |
51 |
52 |
|
Lock Status |
Locked |
Locked |
Locked |
Locked |
Locked |
Not Locked |
Not Locked |
Not Locked |
|
Frequency |
16 MHz |
22 MHz |
29 MHz |
35 MHz |
36 MHz |
105 MHz |
200 MHz |
297 MHz |
|
Symbol Rate |
5120 |
5120 |
5120 |
5120 |
0 |
0 |
0 |
0 |
|
Power Level |
37.0 dBmV |
37.8 dBmV |
38.0 dBmV |
38.0 dBmV |
32.7 dBmV |
28.7 dBmV |
30.5 dBmV |
32.0 dBmV |
|
Modulation |
QAM |
QAM |
QAM |
QAM |
OFDMA |
OFDMA |
OFDMA |
OFDMA |
|
Channel Type |
ATDMA |
ATDMA |
ATDMA |
ATDMA |
TDMA |
TDMA |
TDMA |
TDMA |
Already tried: power-cycling the gateway several times, and connecting a computer directly to the gateway instead of my router. Neither fixed it.
Could an Xfinity employee please:
1. Check the CMTS-side history for my modem since Oct 9: upstream SNR/MER and codeword errors per channel (especially high-band OFDMA 50/51/52), T3/T4 timeouts, partial service, ranging/re-registration events, and any node or plant change around Oct 9.
2. Check for noise or interference in the 105–300 MHz upstream range at my tap, drop and node.
3. Schedule a technician visit, and replace the gateway if the line checks out.
No Responses!