The following are restrictions for Flexible NetFlow: + Traditional NetFlow (TNF) accounting is not supported. + Flexible NetFlow v5 export format is not supported, only NetFlow v9 export format is supported. + Both ingress and egress NetFlow accounting is supported. + Microflow policing feature shares the NetFlow hardware resource with FNF. + Only one flow monitor per interface and per direction is supported.
Reference:
When configuring NetFlow, follow these guidelines and restrictions:
+ Except in PFC3A mode, NetFlow supports bridged IP traffic. PFC3A mode does not support NetFlow bridged IP traffic. + NetFlow supports multicast IP traffic.
The Flexible NetFlow - MPLS Egress NetFlow feature allows you to capture IP flow information for packets that arrive on a router as Multiprotocol Label Switching (MPLS) packets and are transmitted as IP packets. This feature allows you to capture the MPLS VPN IP flows that are traveling through the service provider backbone from one site of a VPN to another site of the same VPN

Reference: https://www.cisco.com/c/en/us/products/collateral/security/advanced-waf-bot-aag.pdf
<Cisco Secure Web Application Firewall (WAF) and bot protection defends your> online presence and ensures that website, mobile applications, and APIs> are secure, protected, and "always on."

See the solution below.
Explanation:
R1
enable
Config t
Int loop0
Ip ospf 1 area 0
Int et0/0
Ip ospf 1 area 0
Ip ospf network point-to-point
copy run start
R2
Enable
Config t
Int loop0
Ip ospf 1 area 0
Int et0/0
Ip ospf 1 area 0
Ip ospf network point-to-point
Int et0/1
Ip ospf 1 area 0
Ip ospf network point-to-point
copy run start
R3
Enable
Config t
Int loop0
Ip ospf 1 area 0
Int et0/1
Ip ospf 1 area 0
Ip ospf network point-to-point
copy run start
Verification:-