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21 Messages

Mon, Jan 18, 2021 7:00 PM

Technicolor CGA4131COM and 6in4 (IPv4 Protocol 41)

Hi,
My 10ish year old SMC D3G-CCR just died, and Comcast came and replaced it with a Technicolor CGA4131COM.  My setup looks like this:

|CGA4131COM| <-> |Linux Router| <-> Switches <->

I have a static /29 assigned to me via comcast,  The first address in that range is the Linux router itself, the next four are used for NATs (Linux router answers ARPs for them), and the last is of course the Comcast router/cablemodem itself.

I had been using a Hurricane Electric 6in4 tunnel (IPv4 Protocol 41) to get IPv6 for my inside devices.  The linux router uses its own IPv4 address to connect to the HE tunnel server endpoint and send the encapsulated IPv6 packets inside IPv4 6in4 packets.  This worked fine when I was using the SMC D3G-CCR, but stopped with the installation of the Technicolor CGA4131COM.

From everything I'm seeing via packet traces, Comcast is blocking 6in4 packets inbound, outbound, or possibly in both directions.

I know that CB has native IPv6 support, but I'm not ready to convert to their ranges yet.  Plus, based on other threads I've seen on this forum, it appears that DHCPv6-PD of the /56 which comcast delegates to the inside router simply doesn't work.

So, can comcast unblock 6in4, or am I boned?

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Contributor

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21 Messages

6 m ago

Firmware details, FYI:

eMTA & DOCSIS Software Version: CM DOCSIS Application - Prod_19.3_d31 & MTA Application - Prod_19.3
Software Image Name: CGA4131COM_4.4p6s2_PROD_sey
Advanced Services: CGA4131COM
Packet Cable: 2.0

Contributor

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21 Messages

6 m ago

Turns out that the Technicolor was blocking 6in4 and no one I talked had a solution for it (apparently no way to reconfig the modem to allow 6in4).

Replaced it with a Netgear, and now everything works again.