"Enable DHCP" on VLAN does not setup a Reserved Dynamic range for secondary (IPv6) subnets

[Trent Lloyd]

When you "Enable DHCP" on a VLAN for the first time, a reserved range for dynamic usage is created. This occurs when enabling DHCP for either a single IPv4 or a single IPv6 subnet on a VLAN.

If you have two subnets on the VLAN, specifically both an IPv4 and IPv6 subnet, a reserved range for the secondary subnet is not request or setup. Only a single reserved range request is shown and made.

This occurs both during initial creation and during reconfiguration.

Version: xenial/main 2.0.0~beta3+bzr4941-0ubuntu1

[Trent Lloyd (lathiat)]

Related to this.. if the IPv6 subnet does not have a gateway, then you actually get a selector for which subnet to use. If you select the IPv4 subnet then nothing else shows, but if you select the IPv6 subnet it asks to enter the gateway.

If both have a gateway the subnet selector does not appear (just rack controller)

This feels related so adding here instead of filing separate, but can file separately if needed.

[Mike Pontillo (mpontillo)]

The "Enable DHCP" drop-down form that appears on the VLAN page is merely a shortcut when configuring your first dynamic range on a VLAN. Subsequent ranges must be added from the subnet details page. (and you'll need the latest beta for that; the one you're using probably didn't yet support editing the ranges from the web UI.)

The goal we have in mind for IPv6 is to not require a dynamic range be specified at all.

IPv6 has the concept of "stateless address auto-configuration" (SLAAC); all IPv6-enabled nodes will automatically get a MAC-based address (called an EUI-64 address). Therefore, the concept of a "dynamic range" in IPv6 has been rendered obsolete by the protocol itself.

Some people will want to disable automatic address configuration and prefer to use DHCPv6. But I believe DHCPv6 can be configured to use the MAC-based EUI-64 addresses by default.

In the end, you'll be able to specify a dynamic range with IPv6 just like you can today with IPv4, but it should not be necessary to do so.

[Mike Pontillo (mpontillo)]

By the way, we're planning on cleaning up IPv6 support for MAAS 2.1, so I'm re-targeting this bug.