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Chapter 5: Configuring the Gateway
The Security Tab
Wireless-G ADSL Gateway
When finished making your changes on this tab, click the Save Settings button to save these changes, or click
the Cancel Changes button 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.
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.
• Key Life Time. In the Key Lifetime field, you may optionally select to have the key expire at the end of a time
period of your choosing. Enter the number of seconds you’d like the key to be used until a re-key negotiation
between each endpoint is completed.
Phase 2
• Encryption. The encryption method selected in Phase 1 will be displayed.
• Authentication. The authentication method selected in Phase 1 will be displayed.
• PFS. The status of PFS will be displayed.
• 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.
Figure 5-26: Advanced VPN Tunnel Setup