Configure IPSec VPN Phase 1 Settings

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If the negotiation fails, it uses Aggressive Mode. All of the above steps should resolve vpn tunnel issues that you are experiencing. For example, in scenarios where a dialup client or dynamic DNS peer connects from an IP address that changes periodically, traffic may be suspended while the IP address changes. To specify a third combination, use the Add button beside the fields for the second combination. First exchange messages 1 and 2 —Proposes and accepts the encryption and authentication algorithms. Sometimes it is crazy that vpn tunnel state is going up and down constantly and users getting frustrated due to connection drop with the servers.

ISAKMP (IKE Phase 1) Negotiations States

Understanding Phase 1 of IKE Tunnel Negotiation

For more information, see Add a Phase 1 Transform. The mode determines the type and number of message exchanges that occur in this phase. This mode is more secure, and uses three separate message exchanges for a total of six messages.

The first two messages negotiate policy, the next two exchange Diffie-Hellman data, and the last two authenticate the Diffie-Hellman exchange. Main Mode supports Diffie-Hellman groups 1, 2, 5, 14, 15, 19, and This mode also allows you to use multiple transforms, as described in Add a Phase 1 Transform.

This mode is faster because it uses only three messages, to exchange data and identify the two VPN endpoints. When you use Aggressive mode, the number of exchanges between two endpoints is fewer than it would be if you used Main Mode, and the exchange relies mainly on the ID types used in the exchange by both appliances.

Aggressive Mode does not ensure the identity of the peer. Main Mode ensures the identity of both peers, but can only be used if both sides have a static IP address.

The Firebox attempts Phase 1 exchange with Main Mode. If the negotiation fails, it uses Aggressive Mode. If you have already upgraded any firmware to the latest version. Sometimes it is crazy that vpn tunnel state is going up and down constantly and users getting frustrated due to connection drop with the servers.

There are couple of reasons that vpn tunnel is getting dropped and it start all of sudden even you have not made any change in the vpn tunnel. In this case, you need to check following things listed as below -: Complete the below mentioned steps for the Phase 1 configuration: Create an access list which defines the traffic to be encrypted and through the tunnel. In this example, the source traffic of interesting subnet would be from the It can contain multiple entries if there are multiple subnets involved between the sites.

In ASA Versions 8. Same an identical Transform Set must be created on the remote end as well. Configure the crypto map, which contains the Following components: Apply the crypto map on the outside interface: VPN-Firewall sh crypto ipsec sa peer AES — A bit block algorithm that uses a bit key.

You can select either of the following message digests to check the authenticity of messages during an encrypted session: MD5 — Message Digest 5.

To specify a third combination, use the Add button beside the fields for the second combination. Select one or more Diffie-Hellman groups from DH groups 1, 2, 5, and 14 through At least one of the Diffie-Hellman Group settings on the remote peer or client must match one the selections on the FortiGate unit.

Failure to match one or more DH groups will result in failed negotiations. Enter the time in seconds that must pass before the IKE encryption key expires. When the key expires, a new key is generated without interrupting service.

The keylife can be from to seconds. If the FortiGate unit will act as a VPN client, and you are using security certificates for authentication, select the distinguished name DN of the local server certificate that the FortiGate unit will use for authentication purposes. If the FortiGate unit is a dialup client and will not be sharing a tunnel with other dialup clients that is, the tunnel will be dedicated to this Fortinet dialup client , set Mode to Aggressive.

This option supports the authentication of dialup clients. It is available for IKE v1 only. Disable — Select if you do not use XAuth. Enable as Client — If the FortiGate unit is a dialup client, enter the user name and password that the FortiGate unit will need to authenticate itself to the remote XAuth server. Dialup clients authenticate as members of a dialup user group. You must first create a user group for the dialup clients that need access to the network behind the FortiGate unit.

Select a Server Type setting to determine the type of encryption method to use between the FortiGate unit, the XAuth client and the external authentication server, and then select the user group from the User Group list.

Enter the user name that is used for authentication. Enter the password that is used for authentication. If you enabled NAT-traversal , enter a keepalive frequency setting. You can use this option to receive notification whenever a tunnel goes up or down, or to keep the tunnel connection open when no traffic is being generated inside the tunnel.

For example, in scenarios where a dialup client or dynamic DNS peer connects from an IP address that changes periodically, traffic may be suspended while the IP address changes. With Dead Peer Detection selected, you can use the config vpn ipsec phase1 tunnel mode or config vpn ipsec phase1-interface interface mode CLI command to optionally specify a retry count and a retry interval. Type a name to identify the Phase 2 configuration.

Select the Phase 1 tunnel configuration. For more information on configuring Phase 1, see Phase 1 configuration. The Phase 1 configuration describes how remote VPN peers or clients will be authenticated on this tunnel, and how the connection to the remote peer or client will be secured.

Define advanced Phase 2 parameters. For more information, see Phase 2 advanced configuration settings below. Select the encryption and authentication algorithms that will be proposed to the remote VPN peer.

You can specify up to three proposals. To establish a VPN connection, at least one of the proposals that you specify must match configuration on the remote peer.

Initially there are two proposals. Add and Delete icons are next to the second Authentication field. Select a symmetric-key algorithms: NULL — Do not use an encryption algorithm. NULL — Do not use a message digest. Replay attacks occur when an unauthorized party intercepts a series of IPsec packets and replays them back into the tunnel.

Enable perfect forward secrecy PFS. Select one Diffie-Hellman group 1, 2, 5, or 14 through This must match the DH Group that the remote peer or dialup client uses. Select the method for determining when the Phase 2 key expires: Seconds , KBytes , or Both.

If you select Both , the key expires when either the time has passed or the number of KB have been processed. Select the check box if you want the tunnel to remain active when no data is being processed.

Enable the option if you want the tunnel to be automatically renegotiated when the tunnel expires. This is available for Phase 2 configurations associated with a dialup Phase 1 configuration. You also need configure a DHCP server or relay on the private network interface.

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Sep 16,  · Re: What is the differnce between Phase 1 and Phase 2 in VPN phanipriyaraju Jan 26, PM (in response to Scott Morris - CCDE/4xCCIE/2xJNCIE) Thanks for your concern. Phase 1 of an AutoKey Internet Key Exchange (IKE) tunnel negotiation consists of the exchange of proposals for how to authenticate and secure the channel. The participants exchange proposals for acceptable security services such as: Encryption algorithms—Data Encryption Standard (DES), triple Data. Step 1: Interesting traffic initiates the IPSec process—Traffic is deemed interesting when the IPSec security policy configured in the IPSec peers starts the IKE process.: Step 2: IKE phase one—IKE authenticates IPSec peers and negotiates IKE SAs during this phase, setting up a secure channel for negotiating IPSec SAs in phase two.