What is a security association SA and how is it used in IPsec?

The concept of a security association (SA) is fundamental to IPSec. An SA is a relationship between two or more entities that describes how the entities will use security services to communicate securely. IPSec provides many options for performing network encryption and authentication.

What is the role of a security association SA in IPsec?

An IPsec security association (SA) specifies security properties that are recognized by communicating hosts. These hosts typically require two SAs to communicate securely. A single SA protects data in one direction. The protection is either to a single host or a group (multicast) address.

What do security associations in IPsec consist of?

Each SA consists of values such as destination address, a security parameter index (SPI), the IPSec transforms used for that session, security keys, and additional attributes such as IPSec lifetime. The SAs in each peer have unique SPI values that will be recorded in the Security Parameter Databases of the devices.

What is SA in tunnel?

The settings that are used for a tunnel are stored in Security Associations (SA). … After an IPsec VPN tunnel is established, any traffic going through the tunnel is sent either as Authentication Header (AH) or Encapsulating Security Payload (ESP) packets.

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Why do we need security association?

A security association (SA) is the establishment of shared security attributes between two network entities to support secure communication. An SA is a simplex (one-way channel) and logical connection which endorses and provides a secure data connection between the network devices. …

What services are provided by IPSec?

Three security services that can be provided by IPSec are: message confidentiality, message integrity and traffic analysis protection. Briefly explain the type of mechanism used to provide each of these services. c. Briefly describe the three major VPN architectures supported by IPSec.

What is Phase 1 and 2 IPSec VPN?

Phase 1 Security Associations are used to protect IKE messages that are exchanged between two IKE peers, or security endpoints. Phase 2 Security Associations are used to protect IP traffic, as specified by the security policy for a specific type of traffic, between two data endpoints.

What are the two modes in which IPSec can be configured to run?

IPSec operates in two modes: Transport mode and Tunnel mode. You use transport mode for host-to-host communications. In transport mode, the data portion of the IP packet is encrypted, but the IP header is not. The security header is placed between the IP header and the IP payload.

How are security associations formed?

Security associations are established between two hosts using either Internet Key Exchange (IKE) [RFC2409] [RFC4306] or Authenticated IP Protocol [MS-AIPS]. These protocols handle the negotiation of the shared state that makes up the security association, as well as authenticating the two hosts to each other.

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What is IPsec sa lifetime?

The default lifetime is 28,800 seconds. The range is from 180 through 86,400 seconds.

What does show crypto IPsec sa do?

A show crypto isakmp sa command shows the ISAKMP SA to be in MM_NO_STATE. This also means that main mode has failed. Verify that the phase 1 policy is on both peers, and ensure that all the attributes match.

Which mode of IPSec should you use?

1. Which mode of IPsec should you use to assure the security and confidentiality of data within the same LAN? Explanation: ESP transport mode should be used to ensure the integrity and confidentiality of data that is exchanged within the same LAN.

What is Phase 1 in IPSec VPN?

VPN negotiations happen in two distinct phases: Phase 1 and Phase 2. The main purpose of Phase 1 is to set up a secure encrypted channel through which the two peers can negotiate Phase 2. When Phase 1 finishes successfully, the peers quickly move on to Phase 2 negotiations.

How do I check my IPSec Phase 1?

To view the IKE Phase 1 management connections, use the show crypto isakmp sa command. Example 19-12 shows sample show crypto isakmp sa output.