rfc9818v1.txt		rfc9818.txt
	Internet Engineering Task Force (IETF) T. Winters		Internet Engineering Task Force (IETF) T. Winters
	Request for Comments: 9818 QA Cafe		Request for Comments: 9818 QA Cafe
	Updates: 7084 July 2025		Updates: 7084 July 2025
	Category: Informational		Category: Informational
	ISSN: 2070-1721		ISSN: 2070-1721
	IPv6 Customer Edge (CE) Routers LAN DHCPv6 Prefix Delegation		DHCPv6 Prefix Delegation on IPv6 Customer Edge (CE) Routers in LANs
	Abstract		Abstract
	This document defines requirements for IPv6 Customer Edge (CE)		This document defines requirements for IPv6 Customer Edge (CE)
	routers to support DHCPv6 Prefix Delegation for distributing		routers to support DHCPv6 Prefix Delegation for distributing
	available prefixes that were delegated to a IPv6 CE router. This		available prefixes to LAN devices that were delegated to a IPv6 CE
	document updates RFC 7084.		router. This document updates RFC 7084.
	Status of This Memo		Status of This Memo
	This document is not an Internet Standards Track specification; it is		This document is not an Internet Standards Track specification; it is
	published for informational purposes.		published for informational purposes.
	This document is a product of the Internet Engineering Task Force		This document is a product of the Internet Engineering Task Force
	(IETF). It represents the consensus of the IETF community. It has		(IETF). It represents the consensus of the IETF community. It has
	received public review and has been approved for publication by the		received public review and has been approved for publication by the
	Internet Engineering Steering Group (IESG). Not all documents		Internet Engineering Steering Group (IESG). Not all documents
	skipping to change at line 93 ¶		skipping to change at line 93 ¶
	prefix delegation requires an IPv6 CE router to sub-delegate IPv6		prefix delegation requires an IPv6 CE router to sub-delegate IPv6
	prefixes based on a set of rules. If more than one router uses		prefixes based on a set of rules. If more than one router uses
	hierarchical prefix delegation, an IPv6 prefix tree is created. When		hierarchical prefix delegation, an IPv6 prefix tree is created. When
	no routing protocol is enabled to discover the network topology, it		no routing protocol is enabled to discover the network topology, it
	is possible to have an unbalanced prefix delegation tree, which leads		is possible to have an unbalanced prefix delegation tree, which leads
	to running out of prefixes. More information on hierarchical prefix		to running out of prefixes. More information on hierarchical prefix
	delegation can be found, e.g., in Section 8.5 of CableLabs IPv6		delegation can be found, e.g., in Section 8.5 of CableLabs IPv6
	eRouter specification [eRouter]. A flat prefix delegation requires		eRouter specification [eRouter]. A flat prefix delegation requires
	the router to be provisioned with the initial prefix and to assign		the router to be provisioned with the initial prefix and to assign
	/64 prefixes to all other prefix requests from routers in the LAN-		/64 prefixes to all other prefix requests from routers in the LAN-
	facing interface. The default configuration of CE router supporting		facing interface. The default configuration of CE routers is
	prefix delegation is designed to be a flat model to support zero-		designed to be a flat model to support zero-configuration networking.
	configuration networking.
	This document does not cover dealing with multi-provisioned networks		This document does not cover dealing with multi-prefix networks with
	with more than one provider. Due to the complexity of a solution		more than one provider. Due to the complexity of a solution that
	that would require routing, provisioning, and policy, this is out of		would require routing, provisioning, and policy, this is out of scope
	scope of this document.		of this document.
	2. Requirements Language		2. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	This document uses these keywords not strictly for the purpose of		This document uses these keywords not strictly for the purpose of
	skipping to change at line 124 ¶		skipping to change at line 123 ¶
	implementers regarding any protocol implementation required to		implementers regarding any protocol implementation required to
	produce a successful CE router that interoperates successfully with a		produce a successful CE router that interoperates successfully with a
	particular subset of currently deployed and planned common IPv6		particular subset of currently deployed and planned common IPv6
	access networks.		access networks.
	3. Terminology		3. Terminology
	The document makes use of the following terms, some of which are from		The document makes use of the following terms, some of which are from
	Section 2 of [RFC8200]		Section 2 of [RFC8200]
	IPv6 node: A device that implements IPv6 protocol.		IPv6 node: A device that implements IPv6.
	IPv6 router: An IPv6 node that forwards IPv6 packets not explicitly		IPv6 router: An IPv6 node that forwards IPv6 packets not explicitly
	addressed to itself.		addressed to itself.
	IPv6 host: An IPv6 node that is not a router.		IPv6 host: An IPv6 node that is not a router.
	ULA: Unique Local Address, as defined in [RFC4193].		ULA: Unique Local Address, as defined in [RFC4193].
	GUA: Global Unicast Address, as defined in [RFC4291].		GUA: Global Unicast Address, as defined in [RFC4291].
	4. IPv6 End-User Network Architecture		4. IPv6 End-User Network Architecture
	The end-user network for IPv6 that is a stub network. Figure 1		The end-user network for IPv6 contains stub networks. Figure 1
	illustrates the model topology.		illustrates the model topology.
	+-----------+		+-----------+
	| Service |		| Service |
	| Provider |		| Provider |
	| Router |		| Router |
	+-----+-----+		+-----+-----+
	|		|
	|		|
	| Customer		| Customer
	skipping to change at line 191 ¶		skipping to change at line 190 ¶
	These requirements are in addition to the ones in Section 4.3 of		These requirements are in addition to the ones in Section 4.3 of
	[RFC7084].		[RFC7084].
	5.1. LAN Prefix Delegation Requirements (LPD)		5.1. LAN Prefix Delegation Requirements (LPD)
	LPD-1: Each IPv6 CE router MUST support IPv6 prefix assignment		LPD-1: Each IPv6 CE router MUST support IPv6 prefix assignment
	according to Section 13.3 of [RFC8415] (Identity Association		according to Section 13.3 of [RFC8415] (Identity Association
	for Prefix Delegation (IA_PD) option) on its LAN		for Prefix Delegation (IA_PD) option) on its LAN
	interface(s).		interface(s).
	LPD-2: IPv6 CE routers MUST assign a prefix from the delegated		LPD-2: Each IPv6 CE routers MUST assign a prefix from the delegated
	prefix as specified by L-2 in Section 4.3 of [RFC7084]. If		prefix as specified by L-2 in Section 4.3 of [RFC7084]. If
	insufficient prefixes are available, the IPv6 CE router MUST		insufficient prefixes are available, the IPv6 CE router MUST
	log a system management error.		log a system management error.
	LPD-3: The prefix assigned to a link MUST NOT change in the absence		LPD-3: The prefix assigned to a link MUST NOT change in the absence
	of a local policy or a topology change.		of a local policy or a topology change.
	LPD-4: After LAN link prefix assignments, the IPv6 CE router MUST		LPD-4: After LAN link prefix assignments, the IPv6 CE router MUST
	keep the remaining IPv6 prefixes available to other routers		keep the remaining IPv6 prefixes available to other routers
	via Prefix Delegation.		via Prefix Delegation.
	LPD-5: IPv6 CE routers MUST maintain a local routing table that is		LPD-5: IPv6 CE routers MUST maintain a local routing table that is
	dynamically updated with leases and the associated next hops		dynamically updated with leases and the associated next hops
	as they are delegated to clients. When a delegated prefix		as they are delegated to clients. Absent explicit
	is released or expires, the associated route MUST be removed		filtering, packets with destination addresses in a delegated
			prefix MUST be forwarded to that prefix regardless of which
			interface they are received on. When a delegated prefix is
			released or expires, the associated route MUST be removed
	from the IPv6 CE router's routing table. A delegated prefix		from the IPv6 CE router's routing table. A delegated prefix
	expires when the valid lifetime assigned in the IA_PD		expires when the valid lifetime assigned in the IA_PD
	expires without being renewed. When a prefix is released or		expires without being renewed. When a prefix is released or
	expires, it MUST be returned the pool of available prefixes.		expires, it MUST be returned the pool of available prefixes.
	LPD-6: By default, the IPv6 CE router filtering rules MUST allow		LPD-6: By default, the IPv6 CE router filtering rules MUST allow
	forwarding of packets with an outer IPv6 header containing a		forwarding of packets with an outer IPv6 header containing a
	source address belonging to Delegated Prefixes, along with		source address belonging to delegated prefixes, along with
	reciprocal packets from the same flow, following the		reciprocal packets from the same flow, following the
	recommendations of [RFC6092]. This updates WPD-5 of		recommendations of [RFC6092]. This updates WPD-5 of
	[RFC7084] to not drop packets from prefixes that have been		[RFC7084] to not drop packets from prefixes that have been
	delegated. IPv6 CE routers MUST continue to drop packets		delegated. IPv6 CE routers MUST continue to drop packets,
	including destination address that is not assigned to the		including destination address, that are not assigned to the
	LAN or delegated.		LAN or delegated.
	LPD-7: The IPv6 CE routers MUST provision IA_PD prefixes with a		LPD-7: The IPv6 CE routers MUST provision IA_PD prefixes with a
	prefix-length of 64 on the LAN-facing interface unless		prefix-length of 64 on the LAN-facing interface unless
	configured to use a different prefix-length by the CE router		configured to use a different prefix-length by the CE router
	administrator. The prefix length of 64 is used as that is		administrator. The prefix-length of 64 is used as that is
	the current prefix length supported by SLAAC [RFC4862]. For		the current prefix-length supported by SLAAC [RFC4862]. For
	hierarchical prefix delegation, a prefix-length shorter than		hierarchical prefix delegation, a prefix-length shorter than
	64 may be configured.		64 may be configured.
	LPD-8: IPv6 CE routers configured to generate a ULA prefix as		LPD-8: IPv6 CE routers configured to generate a ULA prefix as
	defined in ULA-1 of Section 4.3 of [RFC7084] MUST continue		defined in ULA-1 of Section 4.3 of [RFC7084] MUST continue
	to provision available GUA IPv6 prefixes.		to provision available GUA IPv6 prefixes.
	LPD-9: If an IPv6 CE router is provisioning both ULA and GUA via		LPD-9: If an IPv6 CE router is provisioning both a ULA and GUA via
	prefix delegation, the GUA SHOULD appear first in the DHCPv6		prefix delegation, the GUA SHOULD appear first in the DHCPv6
	packets.		packets.
	LPD-10: IPv6 CE routers MUST NOT delegate prefixes via DHCPv6 on the		LPD-10: IPv6 CE routers MUST NOT delegate prefixes via DHCPv6 on the
	LAN using lifetimes that exceed the remaining lifetimes of		LAN using lifetimes that exceed the remaining lifetimes of
	the corresponding prefixes learned on the WAN.		the corresponding prefixes learned on the WAN.
	6. Security Considerations		6. Security Considerations
	This document does not add any new security considerations beyond		This document does not add any new security considerations beyond
End of changes. 12 change blocks.
	21 lines changed or deleted		23 lines changed or added
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