XB6 Bridge Mode and IPV6

Not applicable

I thought I knew what I was doing for the most part, but this IPV6 stuff has thrown me for a loop.

I just updated to the XB6 modem, and the fact that I can't change the DHCP or DNS is silly, so I bridged it to a TP Link Archer C2300.

Now, I can't figure out how to get IPV6 to work.

I have options for Static IP, Dynamic IP (SLAAC/DHCPv6), PPPoE, 6to4 Tunnel, or Pass-Through (Bridge). 

Advanced options include:

IPv6 address from DHCPv6 or SLACC.

Prefix Delegation (Enable or Disable)

And then for the LAN:

Assigned Type:  DHCPv6, SLAAC+Stateless DHCP, SLAAC+RDNSS

Address Prefix:  (box) /64

I've tried a variety of combinations, but can't seem to get anything working.

Can I get IPv6 working when the modem is bridged?

Am I an idiot?  (Or, better question:  How big of an idiot am I?)

Any help would be greatly appreciated.

Thanks!

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31 Replies

Re: XB6 Bridge Mode and IPV6

mjducharme
Grasshopper

Hi,

I don't have Shaw 300 or a TP-Link, but I believe I know the correct config.

Use "Dynamic IP (SLAAC/DHCPv6)"

Under advanced options, you need to enable Prefix Delegation

Under "Assigned Type", use one of the two SLAAC options. If you are running Windows versions earlier than Windows 10, you will need to use SLAAC+Stateless DHCP instead of SLAAC+RDNSS to get the DNS server addresses properly.

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Re: XB6 Bridge Mode and IPV6

Not applicable

Thanks for the reply...

However, it doesn't seem to want to work.

I didn't realize that the XB6 interface could be accessed in bridge mode, so I logged in there.

I don't seem to have a Global Gateway Address (IPv6) assigned, which, from what I'm reading and barely understanding, is what I'm actually needing?

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Re: XB6 Bridge Mode and IPV6

mjducharme
Grasshopper

When the device is in bridge mode it probably does not need any kind of ipv6 address on the gateway itself, so I'm not sure that is the problem. The problem is much more likely with the TP-Link itself.

On the TP-Link, when you enable IPv6 and set the internet connection type to Dynamic IP, what do you see in the IPv6 Address and IPv6 gateway fields below that?

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Re: XB6 Bridge Mode and IPV6

Not applicable

I get an IPv6 address, as well as Primary and Secondary DNS.

I don't actually have a section for a IPv6 Gateway.

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Re: XB6 Bridge Mode and IPV6

mjducharme
Grasshopper

Yes but does the IPv6 address look like a global one? Or does it start with fe80:: (which is just a local non-routeable address)

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Re: XB6 Bridge Mode and IPV6

Not applicable

Sorry, it's a 2604 start.

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Re: XB6 Bridge Mode and IPV6

mjducharme
Grasshopper

OK, then the router itself is getting IPv6 on the WAN interface. On the TP-Link, into System Tools->Diagnostics->ping and ping Google at the address 2607:f8b0:400a:809::200e

I think it will probably reply.

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Re: XB6 Bridge Mode and IPV6

Not applicable

For some reason, I got an "Invalid format" error.  Tried ipv6.google.com and it did reply with essentially the same address you gave me.

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Re: XB6 Bridge Mode and IPV6

mjducharme
Grasshopper

Probably their ping tool just doesn't recognize IPv6 addresses for some silly reason. However this means that your router itself is getting IPv6 connectivity.

The remaining problem then is why your computer is not. Unless you have IPv6 disabled on your computer, the problem is most likely with the Prefix Delegation on the router. What is supposed to happen is the router is supposed to request a prefix from Shaw via DHCPv6 prefix delegation, Shaw gives you a /56 prefix, and the router takes a /64 out of that /56 prefix and assigns it to the LAN port and then your computer gets an address through SLAAC and DNS either through RDNSSS or DHCPv6 other-configuration.

Unfortunately, most home router manufacturers have broken IPv6 prefix delegation and they just don't care to fix it, because to them it is unimportant whether IPv6 actually works. I work for an ISP that provides IPv6 and of the several hundred customers whose home routers request prefixes, only about 1/5 or 1/4 of them actually have any IPv6 traffic, suggesting broken prefix delegation functionality in the router.

For instance, I asked Belkin for a fix only to be told that their routers only support getting IPv6 on the WAN port and do not actually support providing any computers with IPv6 access to the Internet - I asked why they do this and was told that some ISPs will only turn on the connection if the router is capable of IPv6 so they add minimal IPv6 support to the router to make it look to the ISP like IPv6 is working when it is actually broken.

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