Network & Infrastructure / OSPF & Underlay Convergence
OSPF redistribution feedback between two routing domains
A destination survives in routing after its original source disappears because two boundary routers redistribute it back and forth. The apparent redundancy is actually a route feedback loop.
Environment and inputs: OSPFv2 IPv4 underlays, with OSPFv3 explicitly identified where used; timers and diagnostics vary by platform. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Trace route origin, protocol tags, redistribution policy and administrative preference at both boundaries. Record the route after withdrawing the original source in a controlled environment.
Explain the result
Redistribution can erase useful origin context unless policy preserves and checks it. A reimported external copy can falsely keep the prefix alive and attract traffic indefinitely.
Plan the fix
Implement explicit loop-prevention tagging and filtering based on the documented domain design. Keep default origination and aggregate behavior separate from ordinary route redistribution.
Check the result and rollback
Withdraw the source and require the route to disappear everywhere that should lose it. Roll back if filters remove legitimate backup routes, then revise the policy with prefix-specific evidence.