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Forum Discussion
New CAX30, Xfinity Issues
I was using an older Netgear Modem and Netgear Router and Comcast told me it was no longer in their recommendations. For a couple of years they told me I was at the 800Mbps service tier (started off paying for 200Mbps service but they kept increasing this along with the bill), yet all I ever got was 170Mbps dowload. I could easily argue that I was ripped off for several years by Xfinity.
So I decided to update my equipment to something in their recommendations and I installed a CAX30 modem/router. The first couple of days after provisioning I was getting upwards of 700Mbps download and I was satisfied, however that performance quickly disappeared in the third day from installation to the point where 250Mbps is the max I can get on WiFi and oddly enough ethernet performance is more like 100Mbps (thought these were gigabit ethernet ports?).
I looked at the modem log and found several Critical (3) entries. Here's the latest;
UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
The fact that my equipment performed successfully for the first few days after provisioning makes me think this is not a problem inside my home but rather something to do with my neighborhood and/or Xfinity's infrastructure. Seems crazy to be paying Xfinity for "up to 800Mbps" and using high end Netgear equipment with these middling results.
Does the modem's critical message reveal anything and what about the very slow ethernet results?
thanks
14 Replies
What Firmware version is currently loaded?
Please post a copy and paste of the modems connection status and event log page.
https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-modem-modem-router
https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-modem-routerAny Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.
Hardware Version
V1.01
Firmware Version
V2.2.4.2
Cable Firmware Version
V1.04.10
Connection Status
IP Address
xx.xx.xx.xx
2001:558:6017:43:d5fe:6c61:5418:349c
Subnet Mask
xx.xx.xx.xx
128
Default Gateway
xx.xx.xx.xx
fe80::21c:73ff:fe00:99
DHCP Server
0.0.0.0
DNS Server
75.75.75.75, 75.75.76.76
2001:558:feed::1
2001:558:feed::2
Lease Obtained
0 days, 2 hours, 0 minutes, 0 seconds
Lease Expires
0 days, 1 hours, 42 minutes, 19 seconds
Event Log
Time
Priority
Description
2025-05-16 08:14:01
Notice (6)
CM-STATUS message sent. Event Type Code: 24; Chan ID: 194; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=2xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-16 08:12:25
Notice (6)
CM-STATUS message sent. Event Type Code: 16; Chan ID: 194; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-15 14:51:28
Critical (3)
UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-15 14:51:28
Notice (6)
DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-15 14:51:27
Notice (6)
DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:31
Notice (6)
Honoring MDD; IP provisioning mode = IPv6
1970-01-01 00:00:25
Critical (3)
UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:24
Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-14 12:57:11
Critical (3)
UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:26
Critical (3)
UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:24
Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
2025-05-14 10:19:21
Critical (3)
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
There is more down the page for the connection status if you can post that as well.
For the event log, Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.
I suspect what you are looking for is actually under "Cable Connection", however the website doesn't seem to allow me to post the information (size of message limits?)
May need to do a screen print rather than copy/paste.
Details in the .PdF
There we go. Thats it.
So power levels look good, on the low side but with in specs. https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router
Seeing some correctables and should be mostly zeros, not bad but still the modem is having to do some work.Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.
Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended.
Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box.
Be sure your using good quality RG6 coax cable up to the modem.
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.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html
https://highspeed.tips/docsis-events/
Comcast installed a 2-way coax splitter in the upstairs bedroom for the modem/router and a TV. So this is at the absolute longest cable run and they installed two(2) 2-way splitters at the service panel. The cable comes into the house to a 2-way splitter and then 1 run goes straight to the upstairs bedroom where another 2-way splitter services a TV and the Modem/Router. The other leg goes to yet another splitter on the service panel handling the 2 cable TVs on the house's main floor.
What I don't get is how the first 3 days after installing the new Netgear CAX30 Modem/Router, I was getting 600-700Mbps and afterwards went down to 200Mbps on average. To some extent, I would be satisfied with 200Mbps service, however I have been paying for 800Mbps for several years.
