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I am considering purchasing a cable modem in place of renting from my cable internet provider (Brighthouse/Time Warner). To my knowledge This provider uses DOCSIS standards. There is an approved list of cable modem devices listed on their website.

My question is, what would make a particular modem "approved" to work with their system? Is it solely compatibility with DOCSIS 2.0/3.0? Are their other features of a modem beside DOCSIS compliance that would make it compatible?

I am trying to figure out if something like this netgear modem, which is DOCSIS 2.0 & 3.0 compatible, but is not listed on the "approved" modem list, would work on the network.

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I work at an ISP and know that not all modems conform to the standards. It is more hackery then you would think, and lots of times ISPs and modem-manufacturers have to discuss a lot to get it working. So it could be that there are a lot of compatibilityissues besides the DOCSIS-version. If your ISP uses DOCSIS3 make sure your modem supports IPv6, because your ISP may switch soon if they are implementing that. – xatr0z Mar 5 '12 at 14:26
Thank You @xatr0z. That is some interesting insight. maybe i will just stick to the list then :) – Hari Seldon Mar 5 '12 at 14:37
up vote 1 down vote accepted

One of the criteria used for compatibility is that the provider has actually tested the hardware and knows it works. All these devices should be built to a standard in terms of the hardware and firmware (to get the compliance) but this isn't necessarily so. The only way they can guarantee this is if they test the device themselves. As there are far more cable modems on the market than any one provider can reasonably be prepared to test and support it's simpler for them to say

These are the ones we know that work. Anything else may work but we won't support you if you use something not on our list.

This may seem harsh - but to support all possible cable modems wouldn't be cost effective.

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thanks for the response. I get that it is not feasible for any company to test all of the hardware that may be available. My intent with the question though is to focus more on the features of a cable modem. What features of a cable modem could XYZ provider possibly need beyond DOCSIS compliance. Maybe some type of management protocol? I am willing to try an "unsupported modem", if the the supported features are there. Or maybe it doesn't matter at all, because their isn't much variance in cable modem features anyway? – Hari Seldon Mar 5 '12 at 14:31
@HariSeldon - I was trying to point out that there might not be any hardware/software reason behind this. – ChrisF Mar 5 '12 at 14:35
got it... thanks for clarifying – Hari Seldon Mar 5 '12 at 14:38
Implicit in such a supported equipment list is that the listed devices have not found to generate a statistically significant amount of trouble reports, but for legal reasons, the MSO will probably not put up a 'not supported' list. There are many back-office reasons why you might want to purchase the same make and model of cable modem as the MSO themselves are using/leasing/selling: When the MSO makes routine or maintenance updates to cable modem software, it tends to apply to matching hardware, and not whether the modem was purchased from them or not. – Nevin Williams May 24 '13 at 18:38

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