If by "for most purposes" you mean something else than actually using IPv6 in a network.

For one, address allocation is entirely different. Devices will have several addresses, and some of them can be temporary addresses.

If your ISP assigns you dynamic prefixes (mine does), you can end up with devices not being able to connect to the internet after the router/modem reboots, since they're not told about the new prefix you just got from your ISP and happily keeps using the old one.

If your ISP assigns you dynamic prefixes (mine does), dynamic DNS is required for each server box (apparently one can centralize this by using DHCP-PD, but I haven't figured this out for my pfSense router).

And if you're writing an IPv6-enabled application, parsing client/server address input is a PITA compared to IPv4.

The list goes on and on, but these were the major pain points I found while trying to use IPv6 at home, which are non-existent when using IPv4.

But unstable prefixes are not a fundamental problem with IPv6, more of a teething problem where some ISPs may take some time to get clued in.

Meanwhile it never hurts to automate your handling of renumbering, it'll happen eventually anyway - just like letsencrypt short expiration times actually help you avoid cert expiration problems.

> If your ISP assigns you dynamic prefixes (mine does), you can end up with devices not being able to connect to the internet after the router/modem reboots, since they're not told about the new prefix you just got from your ISP and happily keeps using the old one.

You have a broken router setup, it's not doing router advertisement. Every reply of yours in this thread is just you complaining about something that you misconfigured on your router or did not bother reading about in any decent IPv6 introduction. Please stop the FUD.

> If your ISP assigns you dynamic prefixes (mine does)

Well there goes your problem…

Yes it's not what is currently (19 years after IPv6 RFC) considered best practices[1], but that's what my ISP hands me, so that's what I got to work with.

[1]: https://www.ripe.net/publications/docs/ripe-690

Either they really don't understand IPv6 or they are creating a false scarecity to charge you more money for what is essentially a free and virtually infinite resource to them, probably both.

Or they're running 6rd and giving him a dynamic ipv4?

Not sure what they're running. They do hand me a dynamic IPv4 address, but unless the modem is offline for more than an hour or so, I get the same address.

For whatever reason I get a new IPv6 prefix every time the modem or router reboots.

> For most purposes, IPv6 works the same as v4 (only it has bigger addresses: 128-bit instead of 32-bit)

That's the understatement of the year. IPv6 is a huge protocol and its complexity is its main weakness and one of the main reasons people and organizations stay away from it.

This is not true. They changed almost every detail in ipv6, from the address notation, to the fragmentation, to the peer discovery. Some of these may have been improvements, some not. But at the end of the day, all that anyone ever needed was a few more octets on the address. IPv4 with a couple extra dots would have been adopted 15 years ago.

> But at the end of the day, all that anyone ever needed was a few more octets on the address. IPv4 with a couple extra dots would have been adopted 15 years ago.

You are completely ignoring routing issues. IPv6 is designed from the ground up for efficient route aggregation, and more importantly the processes ARIN and RIR use for allocation are based around this. There is no way IPv4 routing would scale to what IPv6 is going to be in 10 years if you "just added" some octets. What are you going to do, force everyone to re-number?

Yeah, remember when IPSec was mandatory? And the two different schemes (never standardized I guess) that would have let you have a "home" IP address and a "network"/real IP address, so if you were streaming a video the source would send to one IP even as you hopped networks? Good times.

> For most purposes, IPv6 works the same as v4

Theoretically yes, in practice not at all. Just one major difference: No NAT any more.

> No NAT any more

The funny thing is, there will be mandatory NAT on the carrier side during transition to IPv6 because of unwillingness of major websites to announce AAAA (including this one). See [0] for some transition method examples. The common theme of these methods is: They spoof DNS to point to fake IPv6 addresses, which is horrible, HORRIBLE, but hopefully motivates IPv4 holdouts to move to IPv6, announce AAAAs.

If you want to see what a wasteland IPv6 still currently is, and why such transition NAT madness will be necessary (sadly): Try disabling IPv4 when you have native IPv6 and your carrier has not enabled such DNS spoofing transition methods yet.

[0] https://en.wikipedia.org/wiki/IPv6_transition_mechanism

Horrible? Sure it's not ideal, but it allows carriers to go IPv6-only on their internal networks. Mobile carriers already put all IPv4 traffic behind a NAT, so this isn't a step backwards.

For most users, the transition will happen via dual-stack (where the customer runs their own IPv4 NAT), not NAT64.

i also disable ipv6 on my servers for abuse purposes, it is to easy to get iv6 addresses

Do you mean you turn off IPv6, because it's easy for others to get lots of IPs and bypass a IP blacklist?

If so, that is a difference from IPv4. Don't block IPs, block subnets. Block the whole /64. It's what you were doing with IPv4 anyway - blocking a whole building / office / etc at once!

That's still no reason to turn IPv6 off in my humble opinion...

IPv6 ratelimiting can be a bit tricky, you block my /64 and I come back with a /48 and so on.

Most stuff defaults to bucketing by /64s.

Right, but how does this differ from IPv4? Every time I restart my cable modem, I get a new IP from a /18 or so of IPv4 space.

IP blocking is far from ideal, in both versions of IP.. IPv6 makes this no better, or worse.

You get a single IP, that doesn’t scale well at all.

Please do not disable IPv6.

Disagree. If you've only got IPv4 experience and have a number of possibly legacy devices on your network, then there is a significant amount of learning and changes required to make it work with IPv6 (securely).

It's entirely reasonable to say "It works fine without [=zero business value], no need to invest that amount of work.". This makes IPv6 a negative value proposition for many orgs.

It depends on the context.

I mostly focus on users of VPN services. It's still rare for them to handle IPv6 traffic. So if you have IPv6 connectivity, IPv6 will leak, bypassing the VPN. Unless you have firewall rules, or disable IPv6 while using the VPN.

>No NAT

I'm in India and my mobile service provider (Jio) is handing out ipv6 addresses. The fascinating thing about this is I was able to access a server hosted on my phone from Internet. Crazy!

Next everyone hosting his/her own website from his/her own smartphone.

I am loving this era.

What phone? And what scope, local or global?

Maybe a firewall would be prudent ;)

Global. OnePlus. But I don't think phone is limiting factor. Any Android should be able to run http server. Plenty are available on play store

It's cool, I'm sure. But I worry about malware apps streaming video surveillance.

Off the top of my head, ARP &. NDP are rather different - NDP is an IP protocol, unlike ARP.