What is the difference between main mode and aggressive?
Main Mode uses a six-way handshake where parameters are exchanged in multiple rounds with encrypted authentication information. Aggressive Mode uses a three-way handshake where the VPN sends the hashed PSK to the client in a single unencrypted message.
Aggressive mode is typically used for remote access VPN's (remote users). Also you would use aggressive mode if one or both peers have dynamic external IP addresses. You don't have to use Aggressive mode however, if the peer devices are using digital certificates.
Main mode or Aggressive mode (within Phase 1 negotiation) authenticate and/or encrypt the peers. Quick mode (Phase 2) negotiates the algorithms and agree on which traffic will be sent across the VPN.
Main Mode ensures the identity of both VPN gateways, but can be used only if both devices have a static IP address. Main Mode validates the IP address and gateway ID. Aggressive Mode is faster but less secure than Main Mode because it requires fewer exchanges between two VPN gateways.
Main mode provides identity protection by authenticating peer identities when pre shared keys are used, and is typically used for site-to-site tunnels. The IKE SA's are used to protect the security negotiations. You should use Main mode when the VPN peers are using static IP addresses.
IKEv2 uses four messages; IKEv1 uses either six messages (in the main mode) or three messages (in aggressive mode). IKEv2 has Built-in NAT-T functionality which improves compatibility between vendors. IKEv2 supports EAP authentication. IKEv2 has the Keep Alive option enabled as default.
IPsec provides more comprehensive security for IP tunneling, while GRE tunnels work well when network teams need to tunnel with multiple protocols or multicast. Generic Routing Encapsulation, or GRE, and IPsec both encase packets, but the two protocols have different requirements...
IKEv1 Phase 2 (Quick Mode) has only three messages. The purpose of IKEv1 Phase 2 is to establish IPSec SA.
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.
The ikev2 protocol has nothing to do with aggressive mode or main mode at all. If you do a "sh crypto isa" it will show you the ikev1 sa and the ikev2 sa.
What are the 2 modes of IPsec operation?
The IPsec standards define two distinct modes of IPsec operation, transport mode and tunnel mode. The modes do not affect the encoding of packets. The packets are protected by AH, ESP, or both in each mode.
Which mode of IPSec should you use to assure security and confidentiality of data within the same LAN? Answer B is correct. ESP transport mode should be used to ensure the integrity and confidentiality of data that is exchanged within the same LAN.
The major difference between an IPsec VPN and an SSL VPN comes down to the network layers at which encryption and authentication are performed. IPsec operates at the network layer and can be used to encrypt data being sent between any systems that can be identified by IP addresses.
Main mode. A Main mode exchange is composed of six messages as shown in Figure 1. Messages 1 and 2 provide agreement on the negotiable attributes of the ISAKMP security association. These associations are used to protect phase 2 negotiations that are established by using this phase 1.
IPSec uses two distinct protocols, Authentication Header (AH) and Encapsulating Security Payload (ESP), which are defined by the IETF. The AH protocol provides a mechanism for authentication only. AH provides data integrity, data origin authentication, and an optional replay protection service.
Network Address Translation-Traversal (NAT-T) is a method for getting around IP address translation issues encountered when data protected by IPsec passes through a NAT device for address translation. Any changes to the IP addressing, which is the function of NAT, causes IKE to discard packets.
IPSec is considered secure and reliable, while IKEv2 is extremely fast and stable – IKEV2 offers quick re-connections when switching networks or during sudden drops. Thus, a combination of IKEv2/IPsec forms one of the best VPN protocols that exhibits the advantages of the two.
IKEv1 phase 1 negotiation aims to establish the IKE SA. This process supports the main mode and aggressive mode. Main mode uses six ISAKMP messages to establish the IKE SA, but aggressive mode uses only three. Therefore, aggressive mode is faster in IKE SA establishment.
Speed: Due to MOBIKE support, IKEv2 is faster and more stable than the other VPN protocols. Security: IKEv2 is the newest VPN protocol which applies IPSec and uses 256-bit encryption.
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GRE vs IPSec : Comparison Table.
| PARAMETER | GRE | IPSec |
|---|---|---|
| Simplicity | Simpler and faster | Complex |
What is ESP protocol used for?
The ESP protocol provides data confidentiality (encryption) and authentication (data integrity, data origin authentication, and replay protection). ESP can be used with confidentiality only, authentication only, or both confidentiality and authentication.
Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network.
Aggressive Mode uses a three-way handshake where the VPN sends the hashed PSK to the client in a single unencrypted message. This is the method usually used for remote access VPNs or in situations where both peers have dynamic external IP addresses.
There are two phases to build an IPsec tunnel: IKE phase 1. IKE phase 2.
Main Mode. Main mode has three two-way exchanges between the initiator and the receiver. First exchange: The algorithms and hashes used to secure the IKE communications are agreed upon in matching IKE SAs in each peer.
IPsec is used for protecting sensitive data, such as financial transactions, medical records and corporate communications, as it's transmitted across the network. It's also used to secure virtual private networks (VPNs), where IPsec tunneling encrypts all data sent between two endpoints.
IPsec VPNs using IKE utilize lifetimes to control when a tunnel will need to re-establish. When these lifetimes are misconfigured, an IPsec tunnel will still establish but will show connection loss when these timers expire.
In Aggressive mode, only three messages are exchanged instead of six messages as in Main mode. Message 1 of Aggressive mode contains all the information that was contained in messages 1 and 3 of Main mode, plus the identity information sent in message 5 of Main mode.
IKEv2 Phases
Like IKEv1, IKEv2 also has a two-phase negotiation process to create a secure tunnel. The first phase of IKEv2 is IKE_SA_INIT and the second phase of IKEv2 is IKE_AUTH.
AnyConnect uses SSL or IKEv2 as the transport protocol. The aggressive mode only applies to IKEv1. So you can disable aggressive mode if you are using AnyConnect as the client.
Can aggressive mode be used in site to site VPN Why?
While Aggressive Mode is faster than Main Mode, it is less secure because it reveals the unencrypted authentication hash (the PSK). Aggressive Mode is used more often because Main Mode has the added complexity of requiring clients connecting to the VPN to have static IP addresses or to have certificates installed.
IKEv1 Phase 1 negotiation can happen in two modes, either using Main Mode or using Aggressive Mode. IKEv1 Phase 1 Main mode has three pairs of messages (total six messages) between IPSec peers. IKE Phase 1 Aggressive Mode has only three message exchanges. The purpose of IKEv1 Phase 1 is to establish IKE SA.
The ikev2 protocol has nothing to do with aggressive mode or main mode at all. If you do a "sh crypto isa" it will show you the ikev1 sa and the ikev2 sa.
In transport mode, the sending and receiving hosts establish a connection before exchanging data. In tunnel mode, a second IP packet is sent in a completely different protocol. This protects data packets from being inspected or modified in transit.
