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I have 2 segments on a lan (one for home stuff, the other for work), using 2 routers like this:

The line comes in to a BT-Business Smart Hub Type A which supplies a wireless lan of 10.1.0.* That's the first segment. IPv6 works fine on that.

The 2nd segment is made by connecting a second router at a lan port (on the BT router) with a static address of 10.1.0.253. This is a Netgear D6400 and it receives that line on its wan port. Its lan side address is 10.1.1.254 and it serves a work segment of 10.1.1.0/24.

All works well with IPv4 but I can't get it to deal with IPv6.

I have tried auto-config, passthrough, 6to4tunnel etc. but to no avail. Without going into ipv6 addresses, can this be answered simply?

Some reading on the web suggests that it is due to prefix delegation or lack of it on the BT Hub. Is my IPv6 problem due to using a BT router, is it ever going to be possible, have I missed something?

Is the simplest answer to replace them both with a decent Draytek that can handle multiple vlans - that way I get my 2 segments, each with IPv6. But could that work the BT Aspire dongle that (theoretically) kicks in with a 4g connection if the line goes down?

user6311673
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2 Answers2

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On my network I've solved this question with manual prefix on 2nd router, using DHCPv6 to stateful connection. I do a limit to range of modem/router without change the prefix (this device not support more then /64 to use DHCPv6), while on 2nd router I use the manually the same of prefix delegation to modem LAN and I've configurated DHCPv6 to stateful with limited range out of modem range.

After DHCPv6 finished, I set on modem a static route to my 2nd DHCPv6 prefix/124 and finish.

Example 1:

Modem IPv6 from ISP: 2001::1;

On modem:

  • Prefix delegation (DHCP-PD) to LAN modem: 2001:1::/64;
  • Set modem LAN address to ::1:1;
  • Set DHCP stateful range between ::1:2 and :1:ff;
  • Set IPv6 static route to 2nd router LAN range (ex: 2001:1::/124) and gateway equal to 2nd router WAN IPv6 address;

On 2nd router:

  • Disable DHCP-PD and set manually equal of modem LAN (if possible, change the subnet value for above then /64 [ex: /124 used on static route]);
  • Set modem LAN address to ::1;
  • Set DHCPv6 stateful range between ::2 and ::ff;

Finished.

Example 2:

  • If supported by 2nd router, enable a NATv6 and use as IPv4.

I hope helped you. (Sorry by English)

Arturbc
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  • This is to you split the ISP network /64 in various others networks (/68 up to /124) to stay in same prefix and known by Internet dynamic routing (OSPF or RIP from Internet gateways). If try use other network prefix without a NATv6, has no route to your new network and not work. – Arturbc May 05 '22 at 03:31
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I think you need a bigger block or more than /64 for multiple routers. You need to request /56 from your ISP and then you can have 256 Vlans.

Saud Iqbal
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  • I doubt that my ISP (BT) would provide me with that. Does anyone have any answers to my original question - can this be done with 2 routers without prefix delegation or should I get a decent Draytek business grade router to provide 2 segments that way? – user6311673 Sep 02 '20 at 09:06