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Chapter 5: Configuring the ADSL Gateway
The Security Tab
ADSL Gateway with 4-Port Switch
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 the more secure of the two. No matter which mode is selected, the VPN Gateway will
accept both Main and Aggressive requests from the remote VPN device. Select Username, then enter the user
name.
• Encryption. Select the length of the key used to encrypt/decrypt ESP packets. There are two choices: DES and
3DES. 3DES is the more secure of the two.
• Authentication. Select the method used to authenticate ESP packets. There are two choices: MD5 and SHA.
SHA is the more secure of the two.
• 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 5-16: Advanced IPSec VPN Tunnel Setup