Flexible NetFlow improves on traditional NetFlow by providing more flexibility and efficiency in collecting and analyzing network flow data. In this specific configuration, the "mode random one-out-of-100" command is used, which means that only one out of every 100 packets is sampled. This leads to reduced CPU and memory utilization (Option A) because fewer packets are being processed. Additionally, because fewer packets are being analyzed (only one out of every 100), the number of packets to be analyzed is significantly reduced (Option D), leading to further efficiencies.
Reference:
Implementing and Operating Cisco Service Provider Network Core Technologies On-Demand E-Learning

The configuration shown indicates that Router 1 is set up with a route-map named "ddos" that matches traffic tagged with "tag 1". The traffic matching this tag is then set to have a next-hop IP of 192.0.2.1 and a local preference of 150. The community is also set to "no export", which means this route will not be advertised to external BGP peers. Since there's no explicit deny statement in the configuration, only traffic with tag 1 and local preference of 150 will be dropped by Router 1 as per the BGP routing policy. Reference: Implementing and Operating Cisco Service Provider Network Core Technologies course materials.

The Time to Live (TTL) security mechanism is a lightweight security feature that can protect against CPU and memory resource exhaustion due to a denial-of-service (DoS) attack. It works by setting a limit on the number of hops (TTL value) that BGP packets can traverse. By configuring neighbor 10.163.83.55 ttl-security hops 2, ISP A ensures that BGP packets received from ISP C must have a TTL value of at least 254 when they reach R1, as BGP packets decrement the TTL by 1 with each hop. This effectively prevents spoofing attacks from outside the directly connected network because any packets spoofed from further away would have a TTL that drops below the threshold before reaching R1.

The correct configuration for deploying VRF on ASBR router R1 to have connectivity over an MPLS VPN inter-AS Option AB network is found in option C. This involves configuring the interface with the commands shown, including setting the interface ethernet, applying IP VRF forwarding, and enabling MPLS BGP forwarding. These steps ensure that the interface is properly configured for VRF and can support MPLS VPN inter-AS communications effectively. Reference := Implementing and Operating Cisco Service Provider Network Core Technologies