Figure 6-20: Advanced Vpn Tunnel Setup - Cisco Linksys BEFVP41 v2 User Manual

EtherFast Cable/DSL VPN Router with 4-Port 10/100 Switch
Advanced VPN Tunnel Setup
From the Advanced Settings 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 Router will accept both Main and Aggressive
requests from the remote VPN device. If a user on one side of the tunnel is using a Unique Firewall Identifier, this should
be entered under the Username field.
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 Lifetime. 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
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 Lifetime. 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.
Other Settings
NetBIOS broadcast. Check the box next to NetBIOS broadcast to enable NetBIOS traffic to pass through the VPN tunnel.
Anti-replay. Check the box next to Anti-replay to enable the Anti-replay protection. This feature keeps track of sequence
numbers as packets arrive, ensuring security at the IP packet-level.
Keep-Alive. Check the box next to Keep-Alive to re-establish the VPN tunnel connection whenever it is dropped. Once the
tunnel is initialized, this feature will keep the tunnel connected for the specified amount of idle time.
Chapter 6: Using The Router's Web-based Utility
The Security tab

Figure 6-20: Advanced VPN Tunnel Setup

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