Network Security (Version1.0) Modules 18 – 19: VPNs Group Test Online

Hint

The two primary protocols used with IPsec are AH and ESP. AH is protocol number 51 and provides data authentication and integrity for IP packets that are exchanged between the peers. ESP, which is protocol number 50, performs packet encryption.

Hint

The Internet Key Exchange (IKE) protocol is a key management protocol standard used when creating an IPsec VPN tunnel. IKE negotiates security associations (SAs) and calculates shared keys.​

Hint

The two modes for IKE Phase 1 are main and aggressive. Main mode takes more time because the identity of the IKE peers are hidden from eavesdroppers.

Hint

During IKE Phase 2, IPsec peers exchange the IPsec security associations (SAs) that each peer is willing to use to establish the IPsec tunnel.

Hint

The crypto map command is used to finish creating the IPsec security policy by doing the following binding the interesting traffic ACL and transform set to the crypto map specifying the IP address of the remote VPN site configuring the Diffie-Hellman group configuring the IPsec tunnel lifetime The crypto map is bound to the S0/0/0 R1 interface.​

Hint

Peers will attempt to negotiate using the policy with the lowest number (highest priority). Peers do not require matching priority numbers. R1 will attempt to use the most secure default policy (policy #1). If R2 has a matching policy, then R1 and R2 can successfully negotiate the IKE Phase 1 ISAKMP tunnel. If there is no agreement to use the most secure default policy, R1 will attempt to use the next most secure policy.

Hint

The crypto map command, along with the name of the policy, is used to bind the interface to the ISAKMP policy created previously. A transform set is configured using the crypto ipsec transform-set command. Interesting traffic between peers forces IKE Phase 1 negotiations to begin. Peers negotiate the ISAKMP SA policy in step 2 of IPsec negotiations.

Hint

While preventing brute-force attacks and other forced decryption concerns, the longer the key length, the harder it is to break. A 64-bit key can take one year to break with a sophisticated computer, while a 128-bit key may take 1019 years to decrypt. Different encryption algorithms will provide varying key lengths for implementation.

Hint

Remote access VPNs can be used to support the needs of telecommuters and mobile users by allowing them to connect securely to company networks over the Internet. To connect hosts to the VPN server on the corporate network, the remote access VPN tunnel is dynamically built by client software that runs on the hosts.

Hint

Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco that encapsulates multiprotocol traffic between remote Cisco routers. GRE does not encrypt data. OSPF is a open source routing protocol. IPsec is a suite of protocols that allow for the exchange of information that can be encrypted and verified. Internet Key Exchange (IKE) is a key management standard used with IPsec.

Hint

Packets in a VPN are encapsulated with the headers from one or more VPN protocols before being sent across the third party network. This is referred to as “tunneling”. These outer headers can be used to route the packets, authenticate the source, and prevent unauthorized users from reading the contents of the packets.

Hint

Remote access VPNs connect individual users to another network via a VPN client that is installed on the user device. Site-to-site VPNs are “always on” connections that use VPN gateways to connect two sites together. Users at each site can access the network on the other site without having to use any special clients or configurations on their individual devices.

Hint

IPsec can secure a path between two network devices. IPsec can provide the following security functions:

• Confidentiality – IPsec ensures confidentiality by using encryption.
• Integrity – IPsec ensures that data arrives unchanged at the destination using a hash algorithm, such as MD5 or SHA.
• Authentication – IPsec uses Internet Key Exchange (IKE) to authenticate users and devices that can carry out communication independently. IKE uses several types of authentication, including username and password, one-time password, biometrics, pre-shared keys (PSKs), and digital certificates.
• Secure key exchange- IPsec uses the Diffie-Hellman (DH) algorithm to provide a public key exchange method for two peers to establish a shared secret key.

Hint

Site-to-site VPNs are static and are used to connect entire networks. Hosts have no knowledge of the VPN and send TCP/IP traffic to VPN gateways. The VPN gateway is responsible for encapsulating the traffic and forwarding it through the VPN tunnel to a peer gateway at the other end which decapsulates the traffic.

Hint

The transform set is negotiated during Phase 2 of the IPsec VPN connection process. The purpose of the transform set is to define what encryption and authentication schemes can be used. The device doing the VPN initiation offers the acceptable transform sets in order of preference, in this case, ESP authentication using DES for encryption or ESP authentication using SHA-HMAC authentication and integrity for the data payload. Remember that ESP provides confidentiality with encryption and integrity with authentication. The ESP-DES-SHA is the name of the transform set. The parameters that follow (esp-des and esp-sha-hmac) are the specific types of encryption or authentication that is supported by the ASA for the VPN tunnel that uses this transform set.

Hint

In order to bring up an IPsec tunnel, an access list must be configured with a permit statement that will identify interesting traffic. Once interesting traffic is detected by matching the access list, the tunnel security associations can be negotiated.

Hint

The transform set is the set of encryption and hashing algorithms that will be used to transform the data sent through the IPsec tunnel. GRE supports multiprotocol tunneling. It can encapsulate multiple OSI Layer 3 protocol packet types inside an IP tunnel. Routing protocols that are used across the tunnel enable dynamic exchange of routing information in the virtual network. GRE does not provide encryption.​

Hint

Two popular algorithms that are used to ensure that data is not intercepted and modified (data integrity) are MD5 and SHA. The command Router1(config-isakmp)# hash sha indicates that SHA is being used. AES is an encryption protocol and provides data confidentiality. DH (Diffie-Hellman) is an algorithm that is used for key exchange. RSA is an algorithm used for authentication.

Hint

The site-to-site VPN is an extension of a classic WAN network that provides a static interconnection of entire networks. Frame Relay would be a better choice than leased lines, but would be more expensive than implementing site-to-site VPNs. The other options refer to remote access VPNs which are better suited for connecting users to the corporate network versus interconnecting two or more networks.

Hint

The show version command displays the status of technology packages on the router. Based on the partial output shown, the router software already includes ipbasek9 and securityk9. The EvalRightToUse parameter shows that the license is active thereby giving access to the cryptographic features, IPsec and ISAKMP, required to create an IPsec VPN.

Hint

IPsec only supports unicast traffic. If multicast traffic needs to travel through a tunnel, a GRE tunnel will need to be configured between the peers.