IPv6 failover with isc-dhcpd-4.3.5?

Tomek Mrugalski tomasz at isc.org
Wed Feb 8 16:35:04 UTC 2017

W dniu 08.02.2017 o 06:48, Paul B. Henson pisze:
> On Tue, Feb 07, 2017 at 07:27:43PM -0800, Craig Leres wrote:
>> We've been using failover with IPv4 for several years and want to use it 
>> for IPv6. Is this even possible? Obvious attempts at a config result in 
>> strange errors.
> Nope. There's no standard for IPv6 DHCP failover, and the ISC DHPC v6
Hopefully that's about to change. See
If you're not familiar with the IETF publication process, the document
concluded its DHC working group phase, was submitted to IESG, which
approved it 6 days ago, but has not sent the announcement yet. It's not
guaranteed this will be published as RFC, but it's looking good so far.

> implementation does not support any. It's not like there's a shortage of
> addresses for ranges ;), we deployed two servers with different
> address allocations and long lease times.
There's no shortage of IPv6 addresses, that's true, but there are other
reasons why failover could be useful. IPv6 prefixes is the primary one.
Another is the avoidance of changing addresses for clients, so long
lived connections are not broken. And there are couple more. Couple more
scenarios are listed in RFC7031.

Now, on to the actual implementation of that standard in dhcpd... that's
a completely different matter. It is not implemented and it's unlikely
that will change, due to intrusive nature and complexity of such
changes. When ISC decides to implement it, Kea will most likely be used
as a base. No firm decisions has been made yet, though.

Tomek Mrugalski

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