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Very useful, but I don’t understand concept 1, “Don’t pick numbers”.
If I’m right, it’s basically saying don’t do stuff manually, just let the computer do it. I kind of disagree with this. All of my fixed devices have a fixed IP that I manually assigned and derived from the original v4 schema I also have. For example 192.168.x.y becomes prefix::y
Am I misunderstanding something?
On one hand you definitely don’t want to be assigning manual/static IPv6 to all your devices because if your prefix ever changes you’ll have to update it everywhere. IPv6 doesn’t really have a concept of private address space (with a few exceptions).
On the other hand most modern IPv6 stacks support dynamic protocols like SLAAC while also assigning a static suffix to the published prefix (e.g. You want :0:0:1234:1 to go to your server, and SLAAC gets the prefix 200x::5678/64 your server would assign itself 200x::5678:0:0:1234:1).DHCPv6 fixes a lot of these headaches for managed networks by allowing you to reserve specific IPv6 for a given DUID.
IMO, your network, do what you want.
I have two jump Raspberry PIs that I have static suffixes so I always know where they are without relying on DNS or whatever.Edit: I apparently misremembered how I had these setup. I use a custom interface up script to take the SLAAC prefix and append the custom suffix to it as a secondary IP.IPv6 does have private spaces. Any prefix beginning with fd is ‘private,’ and (IIRC) there’s a formula to generate the next 40 bits of prefix to minimize the chance of intersections. i.e., you can generate your own internal /48 functionally equivalent to 192.168/16 or 10/8
Don’t know if you can use that with SLAAAC, but it works if you run a dhcpv6 and makes ipv6 feel a lot like ipv4. You have to NAT everything inside &c, but if you already have a functioning internal IPv4 network, IPv6 is just a matter of figuring out which config options need to be changed (eg, dhcp6.name-servers for option domain-name-servers)
Yes, ULA are one of the exceptions I mentioned. It covers fc00::/7 which is fc00 to fdff, though I believe most use just the top half. I use one for an intermediate network between my edge router and my primary firewall to not consume one of my limited /64 networks.
I haven’t played with IPV6 NAT much. I know its use is a bit discouraged as NAT was always designed as a stopgap measure for IPV4 exhaustion. It might be a good option if you need additional space and your ISP doesn’t support additional prefixes. Just keep in mind that if you use these in DNS, they won’t be accessible externally.
if your prefix ever changes you’ll have to update it everywhere
I mean that’s a good point but I’m paying money to not have my prefix changed. If I were to do it the intended way using DNS, how would I set up the DNS to be prefix agnostic? How would I reference devices in the firewall?
Its a bit complicated and depends on your ISPs support level.
If your ISP supports basic IPv6 they will likely use SLAAC or DHCPv6 to advertise the /64 that any directly connected devices, like your router, can use (/64 being the default size for a single LAN segment, even between point-to-point connections). If you have devices behind that router that want to use IPv6, you will need additional prefixes. The most common method nowadays is to use Prefix Delegation (DHCPv6-PD) where your router will ask the upstream router for an additional routeable prefix which you will use on another interface of the router. The RFC for prefix delegation recommends a /48, but many ISPs are not delegating that much. I only get half of a /60 from my ISP’s modem.
If the ISP just provides you a static routeable prefix, then you would just assign that to your router’s interface and enable SLAAC/DHCPv6 to give out that prefix. This would only need to be configured in a single device and is why they don’t recommend hard coding servers and workstations with IPV6 addresses.
Keep in mind that your router will also need a firewall as all of these IPv6 prefixes are routeable and public. While IPV6 space is quite like finding a needle in a haystack, you could still find yourself having a bad day if you treat it like private IPV4 space.
The end result though is that you would setup DNS so that devices register their IPv6 addresses and it just works. There’s also the MDNS protocol that supports IPv6 which will do segment-local resolution for device names.
