Questions on IPv6 deployment

William Herrin bill at
Tue Jan 17 21:01:40 UTC 2017

On Tue, Jan 17, 2017 at 12:48 PM, Michael Still <stillwaxin at> wrote:

That's overall good advice. I quibble with a couple of points:

1. If you plan to use a /126 on a point to point and can't imagine how
you would use a /64 on that point to point, don't allocate a /64. Odds
are that by the time you can imagine some way to use a /64 there, the
details will require you to assign a new block anyway.

Why be concerned about resource consumption? Because it's a good
habit. Don't overdo it, IPv6 is not resource constrained the way IPv4
is, but shrewd use of available resources is a good habit even when
resources are plentiful.

2. Make all your point to points /124. That will work for all your
point to points. Serial or ethernet. Even the ethernets which have two
high-availability routers on both ends along with the failover address
needing a total of 6 IPs plus 1 for your troubleshooting laptop.
Configuring /124 every time allows you to standardize your
configuration, the same way /64 standardizes the netmask on a LAN

One additional point not brought up:

Minimum assignment to a customer: /60. Never ever /64 or /128. How
much more than a /60 you choose as your minimum is up to you. Common
choices are /56 and /48. But never, ever less than a /60.   Your
customer will want to deploy a /64 to each LAN. And there are so many
cases where he'll want to deploy more than one LAN.

I've noticed a lot of hosting providers getting this wrong. Some of
your customers do create VPNs on their VPC you know.

Bill Herrin

William Herrin ................ herrin at  bill at
Owner, Dirtside Systems ......... Web: <>

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