OSPF protocol variant type for this feature-set. Distinguishes which OSPF protocol version and address family this feature-set targets. Set at creation time based on CLI context; cannot be changed after creation. Protocol Types: - ospfv2: OSPF version 2 for IPv4 routing (RFC 2328) - ospfv3: OSPF version 3 for IPv6 routing (RFC 5340) - ospfv3-af-ipv4: OSPFv3 with IPv4 address family (RFC 5838) - ospfv3-af-ipv6: OSPFv3 with IPv6 address family (RFC 5838) CLI Context Mapping: - 'feature-set ospfv2 ' → protocol_type = 'ospfv2' - 'feature-set ospfv3 ' → protocol_type = 'ospfv3' - 'feature-set ospfv3-af-ipv4 ' → protocol_type = 'ospfv3-af-ipv4' - 'feature-set ospfv3-af-ipv6 ' → protocol_type = 'ospfv3-af-ipv6' Immutability: Once set, protocol_type cannot be modified. To change protocol type, delete the feature-set and recreate with the desired protocol_type.