Chapter 5 Quick Setup

5.5.6 VPN Advanced Wizard - Phase 2

Phase 2 in an IKE uses the SA that was established in phase 1 to negotiate SAs for IPSec.

Figure 49 VPN Advanced Wizard: Step 4

•Active Protocol: ESP is compatible with NAT, AH is not.

•Encapsulation: Tunnel is compatible with NAT, Transport is not.

•Encryption Algorithm: 3DES and AES use encryption. The longer the AES key, the higher the security (this may affect throughput). Null uses no encryption.

•Authentication Algorithm: MD5 gives minimal security. SHA-1gives higher security. MD5 (Message Digest 5) and SHA1 (Secure Hash Algorithm) are hash algorithms used to authenticate packet data. The SHA1 algorithm is generally considered stronger than MD5, but is slower.

•SA Life Time: Set how often the ZyWALL renegotiates the IKE SA. A short SA life time increases security, but renegotiation temporarily disconnects the VPN tunnel.

•Perfect Forward Secrecy (PFS): Disabling PFS allows faster IPSec setup, but is less secure. Select DH1, DH2 or DH5 to enable PFS. DH5 is more secure than DH1 or DH2 (although it may affect throughput). DH1 refers to Diffie-Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group 2 a 1024 bit (1Kb) random number. DH5 refers to Diffie-Hellman Group 5 a 1536 bit random number (more secure, yet slower).

•Local Policy (IP/Mask): Type the IP address of a computer on your network. You can also specify a subnet. This must match the remote IP address configured on the remote IPSec device.

•Remote Policy (IP/Mask): Type the IP address of a computer behind the remote IPSec device. You can also specify a subnet. This must match the local IP address configured on the remote IPSec device.

•Nailed-Up: This displays for the site-to-site and remote access client role scenarios. Select this to have the ZyWALL automatically renegotiate the IPSec SA when the SA life time expires.

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ZyWALL USG 50 User’s Guide