Canonicalize IPv6 text before comparing or logging addresses

Use this document to connect an official requirement or behavior to observable evidence: Canonicalize IPv6 text before comparing or logging addresses. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 5952 — A Recommendation for IPv6 Address Text Representation from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• Canonical IPv6 text suppresses leading zeroes in each 16-bit field while representing a single all-zero field as 0. The research record locates this support at Section 4.1 (Handling Leading Zeros in a 16-Bit Field).
• The double-colon form compresses the longest eligible zero run, never a single zero field, and selects the leftmost run when equal-length runs tie. The research record locates this support at Sections 4.2.1-4.2.3 (:: Usage).
• Hexadecimal letters in the canonical representation must be lowercase. The research record locates this support at Section 4.3 (Lowercase).

Keep the evidence boundary at these traced claims. They support a review of address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains; they do not support conclusions outside the source’s stated conditions.

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. Do not read the source as proof of implementation or permission to change production. Its guidance remains conditional on DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring and the environment’s recorded constraints.

Applicability questions

• For source statement 1 at Section 4.1 (Handling Leading Zeros in a 16-Bit Field), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Sections 4.2.1-4.2.3 (:: Usage), which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 4.3 (Lowercase), 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. Anchor the review in the cited section and keep observation separate from interpretation. 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.

If the review warrants change, use a bounded implementation with prerequisites, test population, monitoring, abort criteria, and a rehearsed reversal. Sequence checks for DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring and sanitize protected material before retention.

Verification and evidence

Keep the source locations Section 4.1 (Handling Leading Zeros in a 16-Bit Field); Sections 4.2.1-4.2.3 (:: Usage); Section 4.3 (Lowercase) adjacent to the sanitized artifacts used for comparison. Prefer configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results, with enough identity and timing data for an independent recheck.

Close the review only when the evidence, exception handling, resulting action, and after-state are linked. Schedule a new review after material technical, organizational, incident, or source changes; today’s observation is not a continuing guarantee.

Official references

• RFC 5952 — A Recommendation for IPv6 Address Text Representation — RFC Editor / Internet Engineering Task Force