Govern 32-bit BGP communities as transitive routing policy tags

Use this document to connect an official requirement or behavior to observable evidence: Govern 32-bit BGP communities as transitive routing policy tags. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 1997 — BGP Communities Attribute from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• The BGP COMMUNITIES attribute is optional and transitive and contains a variable-length set of four-octet community values. The research record locates this support at Section COMMUNITIES attribute.
• NO_EXPORT blocks advertisement beyond a confederation, NO_ADVERTISE blocks every peer advertisement, and NO_EXPORT_SUBCONFED blocks external peers including other member ASes inside a confederation. The research record locates this support at Section Well-known Communities.
• A speaker may add or locally modify communities and use them to control which routes it accepts, prefers, or distributes. The research record locates this support at Section Operation.

Do not import neighboring assumptions into the source record. The supported task is a scoped comparison involving address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains and the conditions the source actually describes.

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 COMMUNITIES attribute, which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section Well-known Communities, which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section Operation, 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. Use a two-person review for the source interpretation and the resulting operational decision. 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

Tie each conclusion back to Section COMMUNITIES attribute; Section Well-known Communities; Section Operation and to observable material such as configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results. Preserve provenance and stable identifiers without copying secrets into the evidence set.

Keep before-state evidence, approval, test or change result, exceptions, and after-state evidence together. Use an approved lab, window, or nonproduction path for risky tests. Set a recheck trigger for version, architecture, dependency, vendor, incident, or ownership change. A check proves only what was observed.

Official references

• RFC 1997 — BGP Communities Attribute — RFC Editor / Internet Engineering Task Force