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I'm on the phone with Charter (cable company) about how overnight my network speed went from 30 Mbps to 2 Mbps and this support person swears it's because my modem doesn't support 30 Mbps.

I say she's crazy since for 18+ months I've used this modem with no issue.

So, is it technically possible for a modem to all of the sudden continue to work fine but at a drastically reduced speed?

Modem is a Ubee DOCSIS 2.0 (10C018).

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I'm thinking maybe the modem detected a protocol problem on the cable and is "falling back" to a slower protocol. Have you tried unplugging the modem and plugging it back in? – Daniel R Hicks Jan 15 '12 at 20:11
Another possibility is that they mixed up your modem's serial number with someone else's and the other modem IS limited. But of course they then send your modem the order to limit its rate. – Daniel R Hicks Jan 15 '12 at 20:54
up vote 2 down vote accepted

The specs indicate 30Mbps-42Mbps according to the manuafcturer's Datasheet Possible that the ISP is throttling the link. Here in Canada the ISPs will really throttle based on torrents but not sure in US.

Possible that the modem is defective?

Do you have a router connected? Check the WAN port speed/duplex on that. Have seen Auto/Auto give issues Setting to same speed/duplex on modem and router might be worth checking if you can configure. You may need help from the ISP to configure the modem port

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Connect directly to the ethernet port in the modem and point your browser to There should be some kind of information there about synchronisation speed and signal strength. It is possible that the cable running from the optical to coax converters (probably located somewhere under your street) has an intermittent ground which would cause the signal level to drop. However, all of this is academic and can only satisfy your curiosity. The proper answer is: call your ISP and keep doing that until they fix it.

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