Network & Infrastructure / BGP Policy & Internet Edge
BGP aggregate discard routes and hidden partial reachability
An aggregate remains advertised after every usable component route disappears. Upstream networks continue sending traffic, and the edge's discard route silently absorbs the missing destinations.
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
Inspect aggregate generation conditions, contributing routes, discard entries and policy controlling advertisement. Check each component in the correct routing instance and address family.
Explain the result
Aggregation reduces routing state but also asserts broader reachability. A discard route prevents loops; it does not establish that all addresses inside the aggregate can reach their services.
Plan the fix
Define whether aggregate advertisement should depend on tracked service reachability, component existence or explicit availability policy. Retain necessary loop prevention while correcting the advertisement trigger.
Check the result and rollback
Withdraw individual components and then all components in a controlled test. Verify expected aggregate behavior and rollback if a broader route begins leaking or traffic loops replace the original discard.