Separate IPv6 router discovery, address resolution, and reachability

Use this document to resolve one bounded operational decision: Separate IPv6 router discovery, address resolution, and reachability. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 4861 — Neighbor Discovery for IP version 6 (IPv6) from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• A valid Router Advertisement adds, refreshes, or immediately expires its source in the Default Router List according to the advertised Router Lifetime. The research record locates this support at Section 6.3.4 (Processing Received Router Advertisements).
• Address resolution creates an INCOMPLETE neighbor-cache entry and sends a Neighbor Solicitation to the target’s solicited-node multicast address while queueing at least one packet. The research record locates this support at Section 7.2.2 (Sending Neighbor Solicitations).
• Only upper-layer forward progress or a solicited Neighbor Advertisement confirms forward-path reachability; unsolicited advertisements and Router Advertisements do not. The research record locates this support at Section 7.3.1 (Reachability Confirmation).

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 6.3.4 (Processing Received Router Advertisements), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 7.2.2 (Sending Neighbor Solicitations), which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 7.3.1 (Reachability Confirmation), 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.

Do not move from citation to production in one step. Pilot the decision where practical, observe agreed signals, retain a reversal point, and verify DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring. Handle credentials, keys, recovery data, and personal information through approved secure channels.

Verification and evidence

A reviewer should be able to retrace the decision from Section 6.3.4 (Processing Received Router Advertisements); Section 7.2.2 (Sending Neighbor Solicitations); Section 7.3.1 (Reachability Confirmation) 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.

Preserve both successful and failed observations, along with approval and rollback evidence. Avoid uncontrolled production experiments. Assign an expiry or event-driven recheck so the conclusion is not treated as permanent.

Official references

• RFC 4861 — Neighbor Discovery for IP version 6 (IPv6) — RFC Editor / Internet Engineering Task Force