[Kea-users] yet another question about multiple subnets %)

[perl-list]

> i don't speak english very well, but doesn't it say here that it's possible?
> ----------------
> RFC 8415 DHCP for IPv6 November 2018

> 6.6. Multiple Addresses and Prefixes

> DHCP allows a client to receive multiple addresses. During typical
> operation, a client sends one instance of an IA_NA option and the
> server assigns at most one address from each prefix assigned to the
> link to which the client is attached. In particular, the server can
> be configured to serve addresses out of multiple prefixes for a given
> link. This is useful in cases such as when a network renumbering
> event is in progress. In a typical deployment, the server will grant
> one address for each IA_NA option (see Section 21.4).

> A client can explicitly request multiple addresses by sending
> multiple IA_NA options (and/or IA_TA options; see Section 21.5). A
> client can send multiple IA_NA (and/or IA_TA) options in its initial
> transmissions. Alternatively, it can send an extra Request message
> with additional new IA_NA (and/or IA_TA) options (or include them in
> a Renew message).

This says that the server can assign multiple addresses but the client is in the driver's seat.  Is your WIN10 device asking for multiple IA_NA or IA_TA?  You can check with Wireshark (https://www.wireshark.org/).  It says that by default, the server will allocate only one address.  It wouldn't make sense to send multiple addresses to a client that didn't ask for them.

> The same principle also applies to prefix delegation. In principle,
> DHCP allows a client to request new prefixes to be delegated by
> sending additional IA_PD options (see Section 21.21). However, a
> typical operator usually prefers to delegate a single, larger prefix.
> In most deployments, it is recommended that the client request a
> larger prefix in its initial transmissions rather than request
> additional prefixes later on.

> The exact behavior of the server (whether to grant additional
> addresses and prefixes or not) is up to the server policy and is out
> of scope for this document.

Here it is saying that it is technically possible to send multiple prefix (several /64 lets say).  But, again, that doesn't make sense as you can just allocate a larger than /64 prefix and let the client break it apart as needed.  If your client (WIN10?  Didn't realize WIN10 even cared about prefix delegation) needs multiple networks (subnets), configure your client to ask for a /60 instead of a /64 and your server to allocate anything up to a /60.  Then, it's up to the client to break up the prefix and assign the smaller subnets to the appropriate interfaces.  The ISP router (or whatever) will add a route to your client for the entire prefix and your client will be responsible for what happens after that.