A certificate authority (CA) is a trusted entity that issues digital certificates, which are data files used to cryptographically link an entity with a public key.
Digital certificate contains:
Name of certificate holder.
Serial number which is used to uniquely identify a certificate, the individual or the entity identified by the certificate
Copy of certificate holder’s public key.(used for decrypting messages and digital signatures)
Digital Signature of the certificate issuing authority.
IKEv2 (Internet Key Exchange version 2) is a VPN encryption protocol that handles request and response actions. It makes sure the traffic is secure by establishing and handling the SA (Security Association) attribute within an authentication suite – usually IPSec since IKEv2 is basically based on it and built into it.
DVTIs can provide highly secure and scalable connectivity for remote-access VPNs. The DVTI technology replaces dynamic crypto maps and the dynamic hub-and-spoke method for establishing tunnels.
Dynamic VTIs can be used for both the server and remote configuration. The tunnels provide an on-demand separate virtual access interface for each VPN session. The configuration of the virtual access interfaces is cloned from a virtual template configuration, which includes the IPsec configuration and any Cisco IOS software feature configured on the virtual template interface, such as QoS, NetFlow, or ACLs.
Dynamic VTIs function like any other real interface so that you can apply QoS, firewall, other security services as soon as the tunnel is active. QoS features can be used to improve the performance of various applications across the network. Any combination of QoS features offered in Cisco IOS software can be used to support voice, video, or data applications.