Dual-Stack on SMC D3GCCR and Cisco DPC3939B

Actually @flybynight I' ve run into the same thing; I have aDPC3939B with 5 static v4 addresses. I have multiple Linux routers, and I can copy the DHCP client's configuration for prefix delegation that works on residential service, but it does not work with the DPC. I end up with a 2601: address on the router's WAN, and nothing on the LAN. As well, my DHCPv6 client (the wide client) returns an "XID mismatch" error when attempting to solicit a prefix.

I was gonna ping Comcast_Tuska about it but haven't gotten around to it.

Just rebooted my modem, and indeed it now has an IPv6 address as well as a /64 . 

Is there a way now for my firewall, which is sitting behind the modem, to receive a PD via DHCP? Or is there another way to set this up (hopefully with more then a /64 ...)

I started a dhcpclient on the firewall but its dhcp requests are not answered.

SMC modem with 3.1.6.56 firmware and a linux firewall/router behind it.

Thanks!

The problem may be that the SMC router doesn't work in "bridge" mode?

The router does send out RAs for a 2601.../64, but there are no flags set for managed/other either. I guess the router needs a dhcp relay to make this work, or I could configure my linux routers manually for a prefix assiged to me by comcast, just like I do for the static IPv4 addresses.

I was so excited to finally see IPv6 addresses in the router config 😞

I have the DPC3939B and am seeing the same thing.  When the "IPv6 DHCP Server" is enabled on it, my linux box sees RAs for the /64, but no prefixes.

I have a case open right now - CR411208261 - that has apparently gone to engineering.  I have asked if I can be delegated a /60 so that I have something to distribute to my LAN.  Still waiting for an answer although I know other folks have received at least a /60 PD so I'm not sure what the challenge is other than something with the DPC3939B.

actually, i've begun receiving a /56 with my customer owned SB6141. definitely seems specific to the rental units (DPC3939B, SMCD3G)

So, I noticed that I now have a /64 and PD appearing on my BCI SMC modem (and I do have a static IPv4). Yay!

However, when I attempt to configure my router (running Tomato) to route, I am unable to have the connected clients ping beyond my router.

Details:

I can ping6 to www.google.com, as an exampe, from the router's WAN interface. DHCPv6 does run, and gets the PD, RAs occur from the SMC modem and I get a default route, and the WAN interface sets up a SLAAC autoconf address on the routed /64.

No delegation shows up in the D3GCCR web interface, which is set to enable DHCPv6 and autoconf is enabled for both stateful and stateless addresses.

The Tomato router's inside interface sets up a separate prefix, e.g. if the PD is aaaa:bbbb:cccc:dddd then the inside interface becomes aaaa:bbbb:cccc:ddff and then SLAAC addressing for the last 64 bits. The Tomato router then provides RAs to the LAN behind it on the new prefix. In my mind, this is how V4 works, a router routing between two separate networks, but I'm not sure in V6 if this is correct. Some people have had to add the WAN port to the inside bridge for V6 only. That sounds dangerous as you are then disabling the firewall, as far as I can tell.

If I try to add the routed prefix to the inside interface, and remove the LAN /64 from the WAN interface, I can still ping6 www.google.com, as the routing is happening by Link-local addresses, but internal clients are still not able to ping. I will eventually need to have a public address on the WAN interface, as I need to open ports for my services (BCI).

Is this an issue with how the modem is set-up, or V6 not being fully deployed, or is this my issue, on my router. Any assistance is appreciated, as I'm not 100% sure how routing is supposed to work in this case.

Thanks

If you have a static IPv4 address, can you bring your own router, or are you forced to rent one from Comcast?

Just received word from Engineer via Tier 2 support that my modem is actually being delegated a /56, but the current Cisco software only knows how to take a /64 out of that /56 and make it available on the LAN side.  Until a software update happens, I'm stuck with that.

He just sent me another email saying they hope to have more info a fix this afternoon.

Will post if I hear anything.

SMC and Cisco will receive a /56 for the modem the modem will take the first /64 for it's LAN and sub-prefix delegate a /64..  We are working with the vendor to change the sub-prefix to a /58..

customer owned gear has been setup to receive a /56

Thanks for the reply.  If I understand you correctly, there is actually (2) /64s available on the LAN side of the SMC & Cisco.  One is used by the internal DHCPv6 server, and then another that is a sub-prefix delegated /64.  

If the above is correct, I'm not seeing the sub-prefix delegated /64.  RAs only show the /64 that is setup in the DHCP server.

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@Comcast_Tuska wrote:

SMC and Cisco will receive a /56 for the modem the modem will take the first /64 for it's LAN and sub-prefix delegate a /64..  We are working with the vendor to change the sub-prefix to a /58..

 

customer owned gear has been setup to receive a /56

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I'm seeing /64 on both the modem WAN DHCP and modem LAN. Do I need to hint a /56, or should I just wait for the new modem configurations to catch up?

Thanks

The Cisco DPC3939B sub prefix delegation is not working at this time but the SMC is via a /64..