Cant get IPV6 to work, Comcast, SB6121, and Win7

[FACE89]

I have a Motorola Surfboard SB6121 cable modem connecting Comcast directly to a Win 7 desktop machine via ethernet. Its a garden variety, Realtek on-board ethernet adapter with the latest driver update from 2012. The modem firmware recently updated in Jan 2016. When I look at the SB6121 config page, it says "IPV6 Only" yet IPConfig and every other diagnostic assures me IPV6 is NOT working. When I disable IPV4 protocol on the Network settings page, I lose my internet access altogether. Comcast assures me IPV6 is configured for my home. And IPV6 is reporting with Internet Access on my Xfinity/Arris modem dedicated to my wireless alarm system. Why am I unable to utilize IPV6 with the SB6121?

Thanks in advance,
Paul

 

[bill001g]

Not sure why you would use IPV6 on a modem. Pretty much the IP address is only used to admin the device itself. If you have plugged directly into the modem then your machine talks to the ISP router. The modem is transparent at the IP level.

IPv6 buys you very little in fact it may cut your transfer rates just a bit because of the added header length. Although there are a number of sites that support ipv6 it is not a huge number.

 

[FACE89]

Thank you for your quick response.

Admittedly, I wasn't real clear whether I would gain any benefit from getting ipv6 configured. When my laptop was briefly connected (wirelessly) to the Xfinity/Arris modem/gateway and I happened to run a speedtest (www.speedtest.comcast.net), the ipv6 test yielded a faster transfer rate. But apparently this was just a one-time anomaly.

That said, I connected the same (Win 8.1) laptop to the SB6121 via ethernet and it immediately connected to the internet with both ipv4 and ipv6. So I'm guessing my original issue is related to Win 7 or the adapter driver being used by my desktop machine.

In any case, I'm glad to know there's nothing important to optimize here. Soon enough, both machines will be upgraded to Win 10 and I imagine the issue (as insignificant as it may be) will go away.

Thanks