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ISP provides 64 bit variable prefix to my home network using DHCP-PD.

With IPv4 and NAT I could create stable (fixed subnet) internal network with DHCP, internal DNS and some static routes to subnets with services.

In IPv6 world it gets more complex. Forgive me my ignorance here but what would be the best solution to have dynamically configured clients access services on dynamically configured servers ? Or in other words how can I set up internal services that can be also reached if router (internet connection) is down ?

Does below make sense ?

  • ISP router with SLAAC only
  • additional IPv6 router with specific routes (no default) - is that even possible ?
  • Stateful DHCPv6 for internal computers with ULA
  • DNS server with local zones allowing recursive queries

Alternative idea I have is to configure ULA subnet on ISP router but then how machines on ULA network would be able to access internet ...

Is there away to get away without using NAT on IPv6 protocol ? Some multi node services use IP addresses to configure internal communication and don't like fe80::%interface format. Actually I have hard time to convince Chrome to use it ...

I've read couple of guides how to migrate IPv4 to IPv6 but none of them deal with small home networks that contain services.

Mariusz Zieliński
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  • DNS only, if you want to use prefix detection and add your preferred address. Avoid ULA. – NiKiZe Aug 19 '22 at 05:29
  • Hello. Could you please elaborate ? To be honest I'm struggling with details like correct RA configuration on router. Are you saying that there are DNS servers capable of rewriting prefix part of address ? What about situation when ISP link is down ? – Mariusz Zieliński Aug 19 '22 at 08:44

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I would personally go with ULA.

Use ULA with SLAAC (or DHCPv6 or static addresses, it doesn't matter) for internal services. Add name->ULA address mappings to your internal DNS.

When the router connects to the Internet it will get IPv6 prefix from your provider and will start announcing it through RA to your network. Your nodes will pick it up and configure additional, globally routable, IPv6 addresses on the interfaces. These addresses will be used for connections towards global Internet (more details on this topic in RFC6724).

You won't need NAT for outgoing IPv6.

It may get more complex if you want to expose your internal services to the global IPv6 Internet. You may need then either or both NAT and Dynamic DNS due to the dynamic nature of your prefix delegation.

Tomek
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