Comprehensive and Detailed Explanation

BGP Flowspec allows routers to distributetraffic-filtering rulesusing BGP NLRI.

To enable Flowspec, after neighbors are configured, the essential next step is:

✔Activate the Flowspec address-family under BGP

Example:

router bgp 65000

address-family ipv4 flowspec

neighbor X.X.X.X activate

exit-address-family

This enables:

FlowSpec NLRI exchange

Distribution of drop rules (rate-limit, redirect, null route, etc.)

Automatic ACL/class-map/policy-map generation on edge routers

Why the other options are incorrect:

B. Set BGP routing process→ already done when neighbors were configured

C. Activate neighbors→ only makes senseinsidean address-family; flowspec AF must be enabled first

D. Configure route reflector→ optional and not required for Flowspec to operate

Thus, the correct next step isA. Configure Flowspec for the BGP address-family.