Realistic number of hosts for a /64 subnet?

[Ole Troan]

> On 10 May 2019, at 06:27, Doug Barton <dougb at dougbarton.email> wrote:
> 
> It's been a while since I was configuring subnets, and last time I did the guidance was always no more than 1,000 hosts per subnet/vlan. A lot of that was IPv4 thinking regarding broadcast domains, but generally speaking we kept to it for dual stacked networks, equating an IPv4 /22 with an IPv6 /64. (This was commonly in office environments where we used a subnet per floor to accommodate all of the desktops, printers, phones, tablets, etc.)
> 
> Is this still how people roll nowadays? Have switches and/or other network gear advanced to the point where subnets larger than 1k hosts are workable? In IPv4 or IPv6? I've done quite a bit of web searching, and can't find anything newer than 2014 that has any kind of intelligent discussion of this topic.

In the department of "this is how we should have done it".
I would make the subnets match the physical topology. That is a set of (virtual) point to point links.
That gives one host and one router per link. Which results in a broadcast domain of 2. I wouldn't bother with a shared on-link prefix on the link. Just give the host a set of single addresses. Then you don't have to deal with any of the pesky ND issues, DAD, address resolution and so on.

Best regards,
Ole