This content originally appeared on DEV Community and was authored by Abdulrazzaq Aminu
I was troubleshooting a routing issue in a multi-area OSPF deployment for an enterprise spanning multiple locations. The design included Area 0 (core and internet edge), Area 1 (head office), and Area 2 (a branch office configured as a stub). The branch router in Area 2 was not receiving external BGP-learned routes, preventing access to certain services.
After confirming that the core router was redistributing BGP learned prefixes into OSPF as Type 5 LSAs and verified that Area 2’s stub configuration was filtering them. I reconfigured Area 2 as a Not-So-Stubby Area (NSSA), enabling the ABR to translate Type 5 LSAs into Type 7 LSAs, which are permitted in NSSA areas. To improve route selection, I further changed the external metric type from N2 to N1, allowing internal cost to be considered during path calculations. The branch office regained full external route visibility with improved routing efficiency.
This content originally appeared on DEV Community and was authored by Abdulrazzaq Aminu