Which three items do you recommend for control plane hardening of an infrastructure device? (Choose three)

Enabling unused services expands the attack surface rather than hardening it, contradicting the principle of least functionality required for control plane security.

Warning banners serve a legal and deterrence purpose but do not technically harden the control plane against protocol attacks or CPU exhaustion.

Routing protocol authentication (e.g., MD5 or SHA keychains on OSPF/BGP/EIGRP) prevents injection of malicious routing updates that could redirect or black-hole traffic, directly protecting the control plane routing infrastructure.

Control Plane Policing (CoPP) rate-limits traffic destined to the router CPU, protecting it from denial-of-service and reconnaissance floods that target the control plane processing resources.

Redundant AAA servers improve availability and resilience but are a high-availability measure rather than a direct control plane hardening control.

SNMPv3 provides per-message authentication and optional encryption for SNMP management traffic, replacing the cleartext community strings of SNMPv1/v2c that expose device credentials and configuration data.