DHCPv6 Prefix Delegation Clarification

Thu Jan 19 13:35:10 UTC 2012

Ok - finally received a test client (Dlink router) that would actually ask for a prefix delegation. For anyone who needs the answer to this question, the prefix6 statement is scoped to the shared-network {} block despite what the man page says. If there is no prefix6 statement in the shared-network {} block, the client gets no prefix delegation with the following log message: 

Jan 19 13:25:34 dhcpserver dhcpd: Unable to pick client prefix: no IPv6 prefix pools on this shared network 

even though there was a prefix6 statement in another shared-network {} block. 

----- Original Message -----

> From: "perl-list" <perl-list at network1.net>
> To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> Sent: Monday, January 16, 2012 9:30:46 AM
> Subject: Re: DHCPv6 Prefix Delegation Clarification

> Perhaps a config example would better explain the question regarding
> the scope of the prefix6 statement. Here is an example config:

> shared-network network1 {
> subnet6 1234:0:2E50:E8::/64 {
> range6 1234:0:2E50:E8:1::1 1234:0:2E50:E8:1::ffff;
> #prefix6 low-address high-address / bits;
> #1234:0:2e50:F::/52
> prefix6 1234:0:2e50:f000:: 1234:0:2e50:f900:: /56;
> default-lease-time 600;
> max-lease-time 600;
> min-lease-time 600;
> }
> }

> shared-network network2 {
> subnet6 5678:0:2E50:E8::/64 {
> range6 5678:0:2E50:E8:1::1 5678:0:2E50:E8:1::ffff;
> #prefix6 low-address high-address / bits;
> #5678:0:2e50:F::/52
> prefix6 5678:0:2e50:f000:: 5678:0:2e50:f900:: /56;
> default-lease-time 600;
> max-lease-time 600;
> min-lease-time 600;
> }
> }

> dhcpd -6 does start with the two prefix6 statements in there, and in
> their shared-network location.

> Will users from network1 potentially get a prefix delegation from the
> prefix6 statement in network2 for example? or is it scoped inside
> the shared-network {} block if placed in such a statement, but can
> optionally be global (outside a shared-network block)? This is not
> clear from the man page. Specifically, this line: This statement is
> currently global but it should have a shared-network scope. confuses
> me.

> The prefix6 statement

> prefix6 low-address high-address / bits;

> The prefix6 is the range6 equivalent for Prefix Delegation (RFC
> 3633). Prefixes of bits length are assigned between low-address and
> high-address.

> Any IPv6 prefixes given to static entries (hosts) with fixed-prefix6
> are excluded from the prefix6.

> This statement is currently global but it should have a
> shared-network scope.

> ----- Original Message -----

> > From: "perl-list" <perl-list at network1.net>
> 
> > To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> 
> > Sent: Friday, January 13, 2012 11:53:09 AM
> 
> > Subject: Re: DHCPv6 Prefix Delegation Clarification
> 

> > Does anyone have any information in regards to this question?
> 

> > ----- Original Message -----
> 

> > > From: "perl-list" <perl-list at network1.net>
> > 
> 
> > > To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> > 
> 
> > > Sent: Thursday, January 12, 2012 10:34:03 AM
> > 
> 
> > > Subject: Re: DHCPv6 Prefix Delegation Clarification
> > 
> 

> > > Apologies ... I neglected to include that we are currently
> > > running
> > > version 4.2.3-P1
> > 
> 

> > > ----- Original Message -----
> > 
> 

> > > > From: "perl-list" <perl-list at network1.net>
> > > 
> > 
> 
> > > > To: dhcp-users at lists.isc.org
> > > 
> > 
> 
> > > > Sent: Thursday, January 12, 2012 10:26:35 AM
> > > 
> > 
> 
> > > > Subject: DHCPv6 Prefix Delegation Clarification
> > > 
> > 
> 

> > > > The man page (man 5 dhcpd.conf) states the following regarding
> > > > prefix
> > > > delegation:
> > > 
> > 
> 

> > > > The prefix6 statement
> > > 
> > 
> 

> > > > prefix6 low-address high-address / bits;
> > > 
> > 
> 

> > > > The prefix6 is the range6 equivalent for Prefix Delegation (RFC
> > > > 3633). Prefixes of bits length are assigned between low-address
> > > > and
> > > > high-address.
> > > 
> > 
> 

> > > > Any IPv6 prefixes given to static entries (hosts) with
> > > > fixed-prefix6
> > > > are excluded from the prefix6.
> > > 
> > 
> 

> > > > This statement is currently global but it should have a
> > > > shared-network scope.
> > > 
> > 
> 

> > > > My specific question is in regards to the final statement. Does
> > > > this
> > > > mean that the prefix6 statement can currently be confined to a
> > > > shared-network scope but DHCP will not barf if it is in a
> > > > global
> > > > position, or that it will be global in scope even if placed
> > > > inside
> > > > a
> > > > shared-network scope?
> > > 
> > 
> 

> > > > The reason I ask, is that if it is global even if in a specific
> > > > shared-network statement, invalid networks could be delegated
> > > > to
> > > > clients on completely separate physical networks in our
> > > > implementation.
> > > 
> > 
> 

> > > > Thank you,
> > > 
> > 
> 

> > > > Darren
> > > 
> > 
> 
> > > > _______________________________________________
> > > 
> > 
> 
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> > > 
> > 
> 
> > > > dhcp-users at lists.isc.org
> > > 
> > 
> 
> > > > https://lists.isc.org/mailman/listinfo/dhcp-users
> > > 
> > 
> 
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> > 
> 
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