Posts: 460
Registered: ‎12-16-2007

Re: CM100 Status Page

Downstream SNR shows the strength of the signal to your cable modem as compared to the noise on the line (signal/noise). If the noise level increases the SNR value decreases. So, then high levels are good for the SNR. This number should be at 30 or more. If the SNR goes below 30 than you will probably start to experience some  problems, such as intermittent connection, packet loss, etc.

Downstream Power shows the power of the signal your cable modem is getting. The level of the downstream power should be -15 to 15 dB according to most manufacturers' specs... However, it is best for that level to be in the -8 to 8 range.

Upstream SNR shows how much signal the head end is getting from your cable modem, compared to the noise level. "Head End" refers to the point of reference that is the central point of the local network of your service provider. Anything above 29 is good. Just like the download SNR if the noise level increases the upstream SNR decreases.

Upstream Power shows the level of the signal from the cable modem to the provider. This number should be lower than 55dB. The lower the number, the better your connection.


For more details look at

Posts: 1
Registered: ‎08-19-2009

Re: CM100 Status Page

I think I've discover a "fix" for this.  Apparently the mac assigned to the modem for the ethernet is not accurate.  I have a Cisco router on the inside of the modem and I just created a static arp entry for assigned to the mac address of the cable side of the system (as printed on the bottom of the modem).  It looks to work properly now.
Posts: 1
Registered: ‎10-01-2011

Re: CM100 Status Page

Little late, but figured I would add to this as I was dealing with this god awful model.


Yes it is a router (had to put this in as someone was speaking as though they know everything and are very very wrong - and as such wasted a lot of my time), I checked multiple ways including ipconfig, doing a lot of port checks(after verifying they work with my comcast modem), etc.. Apparently this was done to allow a comp to attached to both the usb and the ethernet connector. There is no way to change any thing on the modem (least as far as I can tell) and it makes life a freaking pain if you are trying to port forward. So far from what I can tell is I can access the internet and I can see the modem at but there is no direct way to open any ports what so ever.

Posts: 1
Registered: ‎05-24-2012

Re: CM100 Status Page

I have a connected problem. My internet is disconnected because the UPSTREAM POWER is 54dbv or above, and the modem shows T3 and T4 issues. A few months ago, there was not connected issue. It has started a few week ago. I directly connect my modem to the wire that COMCAST provides. The UPSTREAM POWER is still 54db. However, I remember 1 years ago, I directly connected my modem to the wire that comcast provide. The UPSTEAM POWER was 40 db and when I connected to the splitter the UPSTREAM POWER was 52 db. I use a 2 way splitter to seperate the TV and the modem linksys CM 100. and I have a amplier to boost the tv signal.  Do you think what cause the UPSTREAM POWER goes up 2 db. It's very annoying because the interest drops off 3-4 times a day.

Posts: 800
Registered: ‎04-22-2012

Re: CM100 Status Page

very common for a splitter to hike up the upstream power and the TV amp you have might just be adding the extra 2db there. an attenuator might be able to help... have you consulted with comcast about this issue?