# Tune IPv6 source and destination selection with explicit policy labels > Use RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6) to review this narrow operational decision without extending the source beyond its stated scope. - Canonical URL: https://update.dsesecurity.com/updates/tune-ipv6-source-and-destination-selection-with-explicit-policy-labels/ - Publisher: Detection Systems & Engineering (DSE Security) - Author: DSE Security Editorial Team - Published: 2026-08-27T12:16:06+00:00 - Modified: 2026-08-27T12:53:57+00:00 - Last reviewed by DSE: 2026-08-26 - Resource type: Playbook - DSE priority: Advisory - Topics: IT, Networks & Infrastructure - Reading time: 3 minutes ## What you need to know Use RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6) to review this narrow operational decision without extending the source beyond its stated scope. ## Potentially affected Teams, systems, services, or facilities within the stated scope of RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6) ## DSE recommendation Compare the observed state with the cited official source, document applicability and exceptions, and test any approved change with rollback safeguards. ## Article Keep this document to one review outcome: Tune IPv6 source and destination selection with explicit policy labels. Only the official source and traced locations below supply facts. Confirm applicability before acting. ## Source fact: The official [RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6)](https://www.rfc-editor.org/rfc/rfc6724.html) from RFC Editor / Internet Engineering Task Force supports the following bounded statements: - The configurable address-selection policy table supplies destination precedence and labels that favor source and destination prefixes with matching labels. The research record locates this support at Section 2.1 (Policy Table). - Candidate sources normally come from the outgoing interface; multicast and unspecified addresses are excluded, and an application-selected address outside the candidate set is an error. The research record locates this support at Section 4 (Candidate Source Addresses). - Source and destination comparisons apply their ordered rules as tie-breakers, including usable scope, deprecation status, matching labels, and common-prefix length. The research record locates this support at Sections 5 (Source Address Selection) and 6 (Destination Address Selection). The source support ends with the statements listed above. Use them to examine address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains in the applicable environment, not to imply a wider guarantee. ## What the source does not establish This RFC evidence supports only the named network-protocol decision; it does not select vendor settings, topology, capacity, or an acceptable failure mode. A correct source interpretation can still be inapplicable to a particular design. Confirm DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring, ownership, and change authority instead of treating documented behavior as a deployment guarantee. ## Applicability questions - For source statement 1 at Section 2.1 (Policy Table), which observable configuration, record, or test can confirm applicability here? - For source statement 2 at Section 4 (Candidate Source Addresses), which observable configuration, record, or test can confirm applicability here? - For source statement 3 at Sections 5 (Source Address Selection) and 6 (Destination Address Selection), which observable configuration, record, or test can confirm applicability here? - Within address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, which versions, roles, and configuration states define the review population? - Could DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring invalidate the test, hide a failure, or change applicability? - Who owns the decision, and which observation requires stopping, escalation, or rollback? ## DSE recommendation: DSE recommends using the cited source as the evidence anchor for this decision. Make the source, asset scope, owner, and expected outcome explicit in the review record. Record the source location, examined part of address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, observed and expected states, owner, and reason for deviation. An implementation decision needs an owner, approved window, prechecks, observable outcome, stop authority, and rollback path. Validate DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring before and after the test, and store only sanitized operational evidence. ## Verification and evidence A reviewer should be able to retrace the decision from Section 2.1 (Policy Table); Section 4 (Candidate Source Addresses); Sections 5 (Source Address Selection) and 6 (Destination Address Selection) through configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results. Record what was collected, where, when, by whom, and which system or role it represents. Retain the starting state, authorization, execution record, outcome, deviation, and final state as one review package. Move disruptive checks to an approved test path. Reopen the decision when versions, design, dependencies, ownership, or official guidance changes. ## Official references - [RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6)](https://www.rfc-editor.org/rfc/rfc6724.html) — RFC Editor / Internet Engineering Task Force ## Primary reference - Name: RFC 6724 — Default Address Selection for Internet Protocol Version 6 (IPv6) - Authority: www.rfc-editor.org - URL: https://www.rfc-editor.org/rfc/rfc6724.html - Source publication date: Not stated by the source ## Citation and use Preferred citation: “Tune IPv6 source and destination selection with explicit policy labels,” DSE Security, https://update.dsesecurity.com/updates/tune-ipv6-source-and-destination-selection-with-explicit-policy-labels/ Publishing principles: https://update.dsesecurity.com/updates/dse-updates-editorial-methodology/ Usage and citation policy: https://update.dsesecurity.com/usage/ Copyright © 2026 Detection Systems & Engineering. 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