IPv6 subnets are supposed to be super cheap. As an individual, through a RIPE LIR, I was able to get a /44 (2^20 /64 subnets), no questions asked. I have these tunneled into my home lab and a couple other locations. I realize my setup is unusual: I have my own ASN and am running BGP.

In most countries you can't even get an ASN as a private individual. I found I couldn't without having a business identity.

FWIW, ARIN will let you register as an individual sole proprietor, even in jurisdictions where this doesn't require state registration/licensing.

If you work with a RIPE LIR, they may be more than willing to help you, even if you are outside of Europe. You just need a "presence" in Europe, which can be virtual (a VPS counts.)

I am in the ARIN region but I did not want to pay the ARIN registration fees for an ASN. It was $550 + $150/year, so I went with a RIPE LIR.

There's no technical reason why you can't if you use active DHCPv6 and other such tricks. They make life harder than standard IPv6, but there's no reason why you can't turn one of your /64s into /120s. With a /56 being the standardised assignment for ISP customers (=256 subnets), I think there's more than enough space for a home network. /48s used to be the recommended space assignment but I think these days you can only get those as a business customer or through an independent party (i.e. Tunnelbroker).

Are you looking to deploy 100 subnets at your house or something? I just don't follow the relation to the /64 size and any hassle.

This sounds like and A/B problem. You’re asking how to do A but what you really want is B. But you’re asking about A because that’s how you think you’d get B in the ipv4 world.

Your ISP should give your router a /56 prefix via PD, which you can divvy up into 256 networks internally. Alternatively, if you don’t need globally-routable addresses, just pick a ULA prefix and have your router advertise it internally.

What happens if your ISP just gives you a /64?

What happens if the moon is made of cheese?

Outside of obscure hypotheticals you make do or switch providers.

It's not that obscure. It's common to be given a /64 to a home, or even to small business premises. Some even get a /128.

So it's reasonable to wonder how people deal with that problem when needing multiple subnets. Many locations don't have a realistic choice of affordable providers, or none of them provide IPv6 with a shorter prefix anyway.

Depends on what you want to do. Maybe use one network or assign static addresses. Here's a post on /120 networks: https://blog.ipspace.net/2011/05/ipv6-neighbor-discovery-exh...

My ISP doesn't even give me a /32 v4 or a /128 v6. CGNAT v4 only.

I'd love to have to make do with a /64.

My ISP did exactly that. I bugged their customer support several times over a month and they finally caved and gave me /60 now.

My ISP gives me /64. It is unusable with consumer routers.

ISPs should do a lot of things, but when it comes to IPv6 many don't. Mine gives me a new prefix every time my router boots. Meanwhile I've had my DHCP allocated IPv4 for 3 years now...

Given that the IPv6 standard was written by enterprise network people with no thought how it would get deployed to the masses, lots of software is still a PITA to work with if you got an ISP like mine.

How does a larger subnet hurt you?

Using /64s can make you vulnerable to NDP exhaustion attacks: http://inconcepts.biz/~jsw/IPv6_NDP_Exhaustion.pdf

Thankfully, contrary to GP's claim, you can just use smaller subnets to mitigate on links where this might be a problem.

What does this have to do with the thread discussion?

It answers the question posed by the parent comment. You asked how using a larger subnet hurts. I provided an example of how using a larger subnet might hurt. How is that irrelevant?