Module Practice and Quiz


What did I learn in this module?

A VPN is virtual in that it carries information within a private network, but that information is actually transported over a public network. A VPN is private in that the traffic is encrypted to keep the data confidential while it is transported across the public network. Benefits of VPNs are cost savings, security, scalability, and compatibility. VPNs are commonly deployed in one of the following configurations: site-to-site or remote-access. VPNs can be managed and deployed as enterprise VPNs and service provider VPNs.

Remote-access VPNs let remote and mobile users securely connect to the enterprise by creating an encrypted tunnel. Remote access VPNs can be created using either IPsec or SSL. When a client negotiates an SSL VPN connection with the VPN gateway, it actually connects using TLS. SSL uses the public key infrastructure and digital certificates to authenticate peers. Site-to-site VPNs are used to connect networks across an untrusted network such as the internet. In a site-to-site VPN, end hosts send and receive normal unencrypted TCP/IP traffic through a VPN terminating device. The VPN terminating device is typically called a VPN gateway. A VPN gateway could be a router or a firewall. GRE is a non-secure site-to-site VPN tunneling protocol. DMVPN is a Cisco software solution for easily building multiple, dynamic, scalable VPNs. Like DMVPNs, IPsec VTI simplifies the configuration process required to support multiple sites and remote access. IPsec VTI configurations are applied to a virtual interface instead of static mapping the IPsec sessions to a physical interface. IPsec VTI can send and receive both IP unicast and multicast encrypted traffic. MPLS can provide clients with managed VPN solutions; therefore, securing traffic between client sites is the responsibility of the service provider. There are two types of MPLS VPN solutions supported by service providers, Layer 3 MPLS VPN and Layer 2 MPLS VPN.

IPsec protects and authenticates IP packets between source and destination. IPsec can protect traffic from Layer 4 through Layer 7. Using the IPsec framework, IPsec provides confidentiality, integrity, origin authentication, and Diffie-Hellman. Choosing the IPsec protocol encapsulation is the first building block of the framework. IPsec encapsulates packets using AH or ESP. The degree of confidentiality depends on the encryption algorithm and the length of the key used in the encryption algorithm. The HMAC is an algorithm that guarantees the integrity of the message using a hash value. The device on the other end of the VPN tunnel must be authenticated before the communication path is considered secure. A PSK value is entered into each peer manually. The PSK is combined with other information to form the authentication key. RSA authentication uses digital certificates to authenticate the peers. The local device derives a hash and encrypts it with its private key. The encrypted hash is attached to the message and is forwarded to the remote end and acts like a signature. DH provides a way for two peers to establish a shared secret key that only they know, even though they are communicating over an insecure channel.

8.4.2 Module Quiz – VPN and IPsec Concepts