Configuring DHCPv6 on a Spectrum Ubee cable modem.

[Spork Schivago]

Hello,

I have a Ubee cable modem that I rent from Spectrum (formerly TWC). It has a DHCPv4 and a DHCPv6 server on it that hands out the IPv4 and IPv6 addresses (respectively). I noticed the addresses from the DHCPv4 server are private. I configured it for the 192.168.2.0 network. I started the pool at 20. I setup some of my clients (printer, Linux box, laptop, gaming consoles, etc) as static.

Then I noticed the DHCPv6 server is handing out public IPv6 addresses. I'm still a bit confused with IPv6 but I'm slowly learning. I wanted to know if it's possible to configure that server to hand out unique-link addresses, from the fc00::/7 network, without anything breaking.

For example, I see in the cable modem's UI System Delegated Prefix and it has the IPv6 global link address (the public ones). I can change that to a user delegated prefix (fc00::/7). I can change what address it starts handing out the IPv6 addresses as. But will this prevent me from accessing the internet with IPv6?

With IPv4, I had to configure the gateway to the private IP address of the cable modem (192.168.2.1). The cable modem doesn't have a DNS server running on it, so when it was set to DHCP, I saw what it had setup for the DNS servers (dns1.rr.com, dns2.rr.com, etc) and I configured my Linux box to use those DNS servers. Will I have to do the same with the IPv6 stuff?

I've tried searching the internet but I couldn't really find a lot of stuff on doing this with OpenSuSE. I can't really find much about the IPv6 and the Ubee modems, at least I couldn't find anything about what I'm trying to do.

Thanks!

[Spork Schivago]

Re: Configuring DHCPv6 on a Spectrum Ubee cable modem.

I think I can do this. I noticed under the Basic >> Setup page, where it lists the DNS servers, it only lists IPv4 DNS servers. The IPv6 DNS server place is blank. From what I can tell, I cannot configure the DNS servers of the cable modem. But I don't think that will be a problem. I think I just need to manually change the IPv6 DHCP System Delegated Prefix from the public IPv6 address prefix to a private one. Then I need to change the pool so it starts giving out addresses starting at something like fc00::20/7. Then I need to configure my PCs and tell them where the gateway is and point them to an IPv6 DNS server and nameserver, preferable owned and operated by Spectrum.

[Spork Schivago]

Re: Configuring DHCPv6 on a Spectrum Ubee cable modem.

Eh, it doesn't work. I change the System Delegated prefix to the fc00::/7 but it doesn't update the
LAN Delegated Prefix, which is grayed out. It says above the LAN Delegated Prefix:

 Server Settings 
 LAN Delegated Prefix will be derived from System Delegated Prefix and Start Address will have the same prefix as the LAN Delegated Prefix.

But changing the System Delegated Prefix doesn't change the LAN Delegated Prefix. And right now, my system is configured to pull an IPv6 address from the DHCPv6 server on the cable modem. It's still pulling the global (public) ones. Maybe if I restart the cable modem, but I doubt it.

[eccerr0r]

Re: Configuring DHCPv6 on a Spectrum Ubee cable modem.

DHCP6 normal mode is very well tied into the uplink IP address for 6rd/6on4/etc., so chances are a lot of GUIs hard codes the address as they're not expecting people to use local unique addresses. What is your v6 provider?

Another issue is if your router set up for NAT6? If not, even if you get DHCP6 local unique address, it won't route them.

If the router is firewalling V6 packets properly, it should not be a security problem to use the global v6 addresses... What problem are you seeing with the global v6 addresses? Just privacy?

[Spork Schivago]

Re: Configuring DHCPv6 on a Spectrum Ubee cable modem.

Our provider is Spectrum. I don't know if the router is setup for NAT6, because the router is built into the modem, and it's a bit limited. But I think it is. I noticed the addresses they hand out for the DHCP is different than the IPv6 WAN address they list in the page. The first four groups are different. So I think it'd have to be doing some sort of NAT6, wouldn't it?

The firewall is the biggest issue and the main reason was privacy. Our only options for the firewall are, "low", "medium", "high". If we had shell access, maybe we'd have something like iptables and we'd be fine. We have some options, like block WAN ping, but if we do that, we cannot ping anyone (probably it's blocking the ICMP-reply). My wife runs Windows 10 on her laptop. I think having that hooked directly to the net is probably a horrible idea.

I was thinking of maybe looking into setting up a Linux box as a gateway and configuring iptables on there. The box would be in the DMZ but if I have the firewall properly setup, security shouldn't be an issue.