A county network team redistributes a classless routing source into OSPF but only classful-looking major networks appear. What missing keyword commonly causes that symptom?

On classic IOS-style OSPF redistribution, the subnets keyword allows classless prefixes (subnetted networks) to be injected into OSPF. Without subnets, redistribution commonly advertises only classful major networks, so a county team redistributing a classless source may see only major-network shapes appear while the expected /24 (or other) county prefixes do not. Adding subnets on the redistribute command is the usual fix for that symptom.

Using match internal on an OSPF stub area filter does not restore classless redistribution into OSPF. Configuring nssa on every ABR facing the county edge is an area type design choice unrelated to the missing classless injection keyword. Setting passive-interface default under the BGP process does not control OSPF redistribution of classless prefixes.

Exam caveat: newer platforms/NX-OS or certain IOS-XE contexts may differ in defaults—know the platform in use—but ENARSI-style questions still treat missing subnets as the classic cause of “only major nets appear.” Even with subnets, route-maps may still filter county prefixes; verify both. Summarization and area ranges can also hide more-specifics; distinguish that from the redistribute keyword issue when troubleshooting.

Operational check: show run | section router ospf and inspect redistribute … lines for subnets. After adding it, show ip ospf database external and show ip route ospf on receivers for the county /24s. Confirm the source protocol table still lists the classless prefixes being redistributed. If majors still appear alongside more-specifics, check whether that is intended summarization versus accidental duplicate injection.