Realistic number of hosts for a /64 subnet?

[Mikael Abrahamsson]

On Thu, 9 May 2019, Doug Barton 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.

It's a good topic to bring up. There has been some work on this in the 
IETF, for instance https://tools.ietf.org/html/rfc8273

This means there is single broadcast domain and single /64 per customer, 
which if properly implemented helps with a lot of the problem space people 
like to solve in this area. It however includes moving away from quite a 
lot of what you call "IPv4 thinking".

I however do not operate wifi networks so I have no idea how widely this 
is implemented in gear available today. If someone else knows, I would 
appreciate if they would share.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se