Dual-Stack on SMC D3GCCR and Cisco DPC3939B

Just a quick follow-up on switching from the SMC to the Netgear modem: I called Comcast this morning, and they had a tech out here by the evening replacing modems. Went overall super smooth. The new modem worked right away with my old IPv4 configuratoin. It took me a bit longer to get IPv6 all set up (the UI isn't all that clear... but I figured it out eventually)... So I got IPv6 working now and all looks good. IPv6 is even a tiny bit faster using the speedtest at http://speedtest.comcast.net .

I have a Cisco DPC3939B with the latest Airport Extreme connected to it and use static ipv4 addresses.  ipv6 works correctly if I connect a computer directly to the Cisco, but when connected to the Airport Extreme, no ipv6 connectivity.   The Cisco DPC3939B shows a /64 Delegated Prefix in the LAN Status page, but the Airport isn't getting an ipv6 address from the Cisco.  (I used this guide http://mydeviceinfo.comcast.net/download.php?file_id=35 except I used a static ipv4 setup.)  Does the Cisco DPC3939B send a DP correctly, or does it have a DP problem like the SMC does? 

you should see a /64 for the cable modem's LAN, and a /56 . A /60 out of this /56 will be assigned to your airport.

 At least that is how it worked for me with my linux router. Here is the (obfuscated) screen shot:

The Cisco DPC3939B modem has a different set of screens, but looking through them I don't see anything referring to a /56. I do see a /64 Delegated Prefix, but I don't see anything regarding a /56 and my airport is definitely not seeing a /60.

I just noticed this evening that my SMC modem now appears to have an IPv6 WAN address and a prefix delegated, so thought I'd try to get it configured with my Tomato router. Having read all of the discussion above it seems that the modem doesn't actually delegate the IPv6 prefixes correctly - I guess I'd be better off getting it swapped to a Netgear if I want native IPv6?

yes. swapping for a Netgear did the trick for me.

This has been my experience so far with ipv6 on these different business class modems

SMC D3GCCR - modem doesn't route the sub-prefix delegation correctly breaking ipv6 connectivity
Cisco DPC3939B - ipv6 works properly for directly attached computers but the sub-prefix delegation isn't working
Netgear CG3000CDR - ipv6 for directly attached computers and sub-prefix delegation for router/firewall work correctly

So far only the Netgear is able to do what I needed for ipv6.  Sorry I didn't record the firmware versions of the SMC or Cisco.  The Netgear I have uses hardware version 1.04 and firmware version V3.01.04.

Still wondering what's up with the SMC. Is it going to be addressed, or should I move to the Netgear?

Thanks

I'm not sure I am hitting the same issue mentioned in this thread or not... 

I have a SMC D3GCCR here, and my Linux Firewall correctly gets a ipv6 address and sees a /64 prefix and all that works fine. 

However, I don't seem to be able to get any other prefix from the router. 

dhclient -v -6 -d gives me only: 

PRC: Soliciting for leases (INIT).
XMT: Forming Solicit, 0 ms elapsed.
XMT: X-- IA_NA 21:40:e9:7c
XMT: | X-- Request renew in +3600
XMT: | X-- Request rebind in +5400
XMT: Solicit on cable, interval 1080ms.
XMT: Forming Solicit, 1080 ms elapsed.

I can't seem to login to the SMC. I suppose I need to call to get them to reset the login on it? 

(Side note: is there any email or web based way to submit requests to comcast business support? Calling all the time takes up a lot of time, especially when the request isn't urgent). 

Thanks for any tips or pointers. 

My hunch is that the vendors are waiting for full static v6 to roll out fixes for these numerous problems.

Yes, prefix delegation and v6 routing are both broken/MIA on the SMC. We've been waiting for a couple of months for a fix...so far no word on if it's coming or not.

Thanks

My guess is that the SMC designers never intended the device to be deployed with both an RG and Dynamic configuration simultaneously. The decision to deploy statically or dynamically would seem to apply to both v4 and v6.

The SMC works fine if you don't delegate and just attach a v6 client to the LAN side of the gateway.

I wouldn't be surprised to see the SMC dropped off the compatibility list moving forward if this issue lags too far behind the curve.

Thanks

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@waitingforv6 wrote:

I wouldn't be surprised to see the SMC dropped off the compatibility list moving forward if this issue lags too far behind the curve.

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Yeah, with the SMC only having 4-channels downstream (meaning it's not compatible with 150mbps+ speed tiers) I imagine the unit will be end-of-lifed soon, so the motivation to fix these v6 problems probably isn't high.

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@train_wreck wrote:

My hunch is that the vendors are waiting for full static v6 to roll out fixes for these numerous problems.

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The only problem with that is Comcast cant move forward with the IPv6 upgrade while 2/3 of the modems (Smc and Cisco) in use are not compatible with the standard.

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@Tnelsom wrote:

The only problem with that is Comcast cant move forward with the IPv6 upgrade while 2/3 of the modems (Smc and Cisco) in use are not compatible with the standard.

 

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If SMC up-revs the model that BCI deploys, I'm sure they will notify people that they need to upgrade. Sometime the hardware just won't cut it any longer and you don't find out until the middle of a project. Murphy's law.

I would just wish that a timeline to resolution would be communicated. The BCI IPv6 rollout appears to be a very low priority to Comcast, but for us who need the service it has a high priority. For my needs, Sonic.net is not only cheaper, but has working v6 and fewer of the niggles that are present in BCI. Possibly time to make a move.

Thanks