Network & Infrastructure / BGP Policy & Internet Edge
Trace BGP import and export policy as separate decision points
A prefix appears on the local edge but never reaches a downstream neighbor. Operators often inspect only the route map they most recently changed and miss an earlier import rejection.
Environment and inputs: BGP speakers and route reflectors; policy syntax, RPKI integration and address-family behavior depend on the implementation. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Capture pre-policy routes where supported, accepted routes, selected paths and advertised routes for the exact address family. Preserve policy sequence numbers and the communities present at each stage.
Explain the result
A route can pass import and still fail export because it is not selected, matches an explicit deny or lacks an expected community. An established peer proves none of these checks.
Plan the fix
Construct a prefix-specific policy trace and correct the first demonstrated mismatch. Use a lab or supported policy evaluation facility before applying the smallest required change.
Check the result and rollback
Verify the intended advertisement from the receiving neighbor as well as the sender. Compare total advertised counts and forbidden test prefixes; restore the previous policy if scope expands unexpectedly.