Advertise BGP capabilities in OPEN before using an optional feature

Treat this document as a focused evidence review: Advertise BGP capabilities in OPEN before using an optional feature. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 5492 — Capabilities Advertisement with BGP-4 from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• A BGP speaker advertises supported capabilities in the Capabilities Optional Parameter of its OPEN message. The research record locates this support at Section 3 (Overview of Operations).
• A capability may be used on a peering only after both peers have advertised support for it. The research record locates this support at Section 3 (Overview of Operations), bilateral advertisement rule.
• An unrecognized received capability must be ignored; it must not trigger an Unsupported Capability notification or terminate the session. The research record locates this support at Sections 3 (Overview of Operations) and 5 (Extensions to Error Handling).

Only the traced statements above are asserted as source facts. Apply the review to address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains after confirming that the source and deployed context match.

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 3 (Overview of Operations), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 3 (Overview of Operations), bilateral advertisement rule, which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Sections 3 (Overview of Operations) and 5 (Extensions to Error Handling), 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. Begin by recording scope and current state before deciding whether a change is warranted. 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

Build a reproducible chain from Section 3 (Overview of Operations); Section 3 (Overview of Operations), bilateral advertisement rule; Sections 3 (Overview of Operations) and 5 (Extensions to Error Handling) to the observed environment. Useful domain evidence includes configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results; label every item with scope, timestamp, collector, and stable identifier.

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 5492 — Capabilities Advertisement with BGP-4 — RFC Editor / Internet Engineering Task Force