According to SAFE IPSec VPN, which of these are recommended design guidelines for maintaining high availability? (Select three.)

A.
When using VPN routers at the headend, use IKE keepalives for high availability.

B.
When using VPN Concentrators or VPN firewalls at the headend, use IKE keepalives for high availability.

C.
Regardless of the high-availability mechanism chosen, a headend device should not be deployed in a configuration that results in CPU utilization higher than 50 percent after failure.

D.
Regardless of the high-availability mechanism chosen, a headend device should not be deployed in a configuration that results in CPU utilization higher than 75 percent after failure.

E.
Cisco recommends running IKE keepalives in combination with routing protocols for resilience to assist in keeping the state current.

F.
Cisco does not recommend running IKE keepalives in combination with routing protocols for resilience to assist in keeping the state current.