Question Spectrum IPv6 Address with BYO Cable Modem

Jun 6, 2020
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Utilizing a DOCSIS 3.0 CM (Hitron Tech / ZyXEL BRG-35503) with Spectrum. The modem is not on their compliant list. The CM is getting a private 10.0.0.0/8 Spectrum IPv4 WAN address but not a IPv6 address. Likewise systems (Windows 10, Ubuntu 20, OpenWrt) directly wired to the CM obtain a public IPv4 address but no public IPv6 address.

The CM appears to be configured with MEMO and MdCfgIpProvMode set to MDD.

Spectrum has stated they provide IPv6 (dual-stack actually) in my area. When pressed, they find it difficult to support this statement.

Looking for guidance on debugging this issue. Is there a way to determine if the CMTS is DOCSIS 3.0 or greater compliant and configured to support dual-stack? Are there other configuration parameters of the CM that I should be attempting to examine and possibly set? Are there logs that can be viewed or network traffic that can be examined to gain further insight?
 

beers

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Probably a device or profile limitation, assuming they have v6 implemented. That modem is pretty old though.

worst case you can roll a 6to4 tunnel
 
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kanewolf

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Utilizing a DOCSIS 3.0 CM (Hitron Tech / ZyXEL BRG-35503) with Spectrum. The modem is not on their compliant list. The CM is getting a private 10.0.0.0/8 Spectrum IPv4 WAN address but not a IPv6 address. Likewise systems (Windows 10, Ubuntu 20, OpenWrt) directly wired to the CM obtain a public IPv4 address but no public IPv6 address.

The CM appears to be configured with MEMO and MdCfgIpProvMode set to MDD.

Spectrum has stated they provide IPv6 (dual-stack actually) in my area. When pressed, they find it difficult to support this statement.

Looking for guidance on debugging this issue. Is there a way to determine if the CMTS is DOCSIS 3.0 or greater compliant and configured to support dual-stack? Are there other configuration parameters of the CM that I should be attempting to examine and possibly set? Are there logs that can be viewed or network traffic that can be examined to gain further insight?
My interpretation is that if the modem isn't on the supported list, then you shouldn't expect it to work.
 
Jun 6, 2020
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Probably a device or profile limitation, assuming they have v6 implemented. That modem is pretty old though.

worst case you can roll a 6to4 tunnel
Had been using HE 6to4 under a previous DOCSIS 2.0 CM. But yes will fall back to HE 6to4 if I'm not able to figure out the DOCSIS 3.0 CM IPv6 issue.
 
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Jun 6, 2020
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That's my thoughts as well because it's not getting a specific configuration file and a generic one instead.
My interpretation is that if the modem isn't on the supported list, then you shouldn't expect it to work.
Yes, not being on the supported list is rarely a good sign. Was pleased it worked at all. Having said that though, it did seem that there might be a way of getting IPv6 working with the proper CM configuration given that it is DOCSIS 3.0 (assuming there is really IPv6 support from upstream).

Looking through the configfile on the CM I'm not seeing anything that immediately jumps out at me as pertaining to IPv6, DPM, MDD or IP provisioning in general. My impression from the MULPI Spec (and other sources ) is that the IP provisioning mode is via the MDD message and not the configfile. Easy to go astray here though.

Could always rent for a month or pickup a used supported device just to confirm IPv6 availability from upstream but what fun is that. It may come to this however.
 
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Jun 6, 2020
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You've definitely gone deep into this for sure. What's the use case that you need ipv6?
Looking to eliminate NAT (perhaps not entirely at first). Anticipating slightly better performance and a simplified network configuration. We'll see. ipv4 with NAT works for now, just not ideal. And then there is still 6to4.
 
Jun 6, 2020
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Quick update.

Use of Spectrum supplied CM DPC3216 resulted in the assignment of dual-stack IP addresses.

Seeing if I can't get configuration information from the DPC3216 to apply to the ZyXEL BRG-35503.
 

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