I'm new to IPv6 and having some issues with a configuration that was really easy/common with IPv4.

My setup looks like this:

WAN (ISP managed router) <-> Router 1 ( my internal router ) <-> My workstations/devices

With IPv4 I would assign private IPs for my workstations/Router 1 (Eg.: in subnet, Router 1 would also have another private IP with my ISP Router in another subnet ( Eg.: ) and with NAT everything would work normally.

Now, with IPv6, the ISP router receives and advertise a /64 IPv6 block. I was able to use dhcp6 client in Router 1 to receive the prefix and then use IPv6 autoconf to allow my workstations to get their IPv6 from that /64 block.

Internally, workstations can ping each other and Router 1, but they can't access the internet.

After contacting my ISP, I was informed that with a /64 block I would only be able to use IPv6 if my workstations were connected directly to the ISP router. And, to make my setup work, I would need another /64 block. Is it true? If so, why? ( their support couldn't explain the reason )

Aren't there another alternatives in this case?

2 Answers 2


Yes, IPv6 uses one /64 per LAN. Your ISP should give you a /48 or at least a /56. They get plenty of addresses from their RIR and they should distribute them properly. The whole idea behind IPv6 is to give everybody plenty of addresses, and ISPs that give you only a /64 are screwing it up...


It's possible but messy.

While IPv6 proponents strongly encourage use of /64 subnets it is possible to use smaller ones and allocate addresses by DHCPv6. You can then use proxy NDP on your router to pick up traffic from the ISPs router so it can be routed to your internal subnets.

Another option is to use NAT. The IPv6 proponents don't like NAT but that doesn't make IPv6 NAT impossible. Linux added support for IPv6 NAT in 3.7.

In an ideal world ISPs would provide their clients with a prefix to route as needed on their internal networks. Sadly that doesn't always seem to be the case, some only allocate a single /64, others allocate a /56 to the home router but don't provide any facilities for actually using it.

This is particularly likely to be an issue for power users and small buisnesses who use "broadband" type internet connections but want to split up their internal networks.

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