Linksys AG241 manual Advanced VPN Tunnel Setup, Key Management, Status, Phase

Chapter 2

Configuration

Key Management

Select Auto (IKE) or Manual from the drop-down menu. The two methods are described below.

Auto (IKE)

Select Auto (IKE) and enter a series of numbers or letters in the Pre-shared Key field. Based on this word, which MUST be entered at both ends of the tunnel if this method is used, a key is generated to scramble (encrypt) the data being transmitted over the tunnel, where it is unscrambled (decrypted). You may use any combination of up to 24 numbers or letters in this field. No special characters or spaces are allowed. In the Key Lifetime field, you may select to have the key expire at the end of a time period. Enter the number of seconds you’d like the key to be useful, or leave it blank for the key to last indefinitely. Check the box next to PFS (Perfect Forward Secrecy) to ensure that the initial key exchange and IKE proposals are secure.

Manual

Select Manual, then select the Encryption Algorithm from the drop-down menu. Enter the Encryption Key in the field (if you chose DES for your Encryption Algorithm, enter 16 hexadecimal characters, if you chose 3DES, enter 48 hexadecimal characters). Select the Authentication Algorithm from the drop-down menu. Enter the Authentication Key in the field (if you chose MD5 for your Authentication Algorithm, enter 32 hexadecimal characters, if you chose SHA1, enter 40 hexadecimal characters). Enter the Inbound and Outbound SPIs in the respective fields.

Manual Key Management

Status

The status of the connection is shown.

Click Connect to connect your VPN tunnel. Click View Logs to view system, UPnP, VPN, firewall, access, or all logs. Click Advanced Settings and the Advanced IPSec VPN Tunnel Setup screen will appear.

System Log

When you have finished making changes to the Security > VPN screen, click Save Settings to save the changes, or click Cancel Changes to undo your changes.

Advanced VPN Tunnel Setup

From the Advanced IPSec VPN Tunnel Setup screen you can adjust the settings for specific VPN tunnels.

Advanced VPN Tunnel Setup

Phase 1

Phase 1 is used to create a security association (SA), often called the IKE SA. After Phase 1 is completed, Phase 2 is used to create one or more IPSec SAs, which are then used to key IPSec sessions.

Operation Mode  There are two modes: Main and Aggressive, and they exchange the same IKE payloads in different sequences. Main mode is more common; however, some people prefer Aggressive mode because it is faster. Main mode is for normal usage and includes more authentication requirements than Aggressive mode. Main mode is recommended because it is more secure. No matter which mode is selected, the VPN Gateway will accept both Main and Aggressive requests from the remote VPN device.

Encryption  Select the length of the key used to encrypt/ decrypt ESP packets. There are two choices: DES and 3DES. 3DES is recommended because it is more secure.

Authentication  Select the method used to authenticate ESP packets. There are two choices: MD5 and SHA. SHA is recommended because it is more secure.

Group  There are two Diffie-Hellman Groups to choose from: 768-bit and 1024-bit. Diffie-Hellman refers to a cryptographic technique that uses public and private keys for encryption and decryption.

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