ZyXEL P-2602HW-D3A User Guide - Page 239
Manual Key Setup, Configuring Manual Key
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P-2602H(W)(L)-DxA Series User's Guide Table 88 Advanced VPN Policies LABEL DESCRIPTION Authentication Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and Algorithm SHA1 (Secure Hash Algorithm) are hash algorithms used to authenticate packet data. The SHA1 algorithm is generally considered stronger than MD5, but is slower. Select MD5 for minimal security and SHA-1 for maximum security. SA Life Time Define the length of time before an IKE SA automatically renegotiates in this field. (Seconds) It may range from 60 to 3,000,000 seconds (almost 35 days). A short SA Life Time increases security by forcing the two VPN gateways to update the encryption and authentication keys. However, every time the VPN tunnel renegotiates, all users accessing remote resources are temporarily disconnected. Encapsulation Select Tunnel mode or Transport mode from the drop-down list box. Perfect Forward Perfect Forward Secrecy (PFS) is disabled (NONE) by default in phase 2 IPSec Secrecy (PFS) SA setup. This allows faster IPSec setup, but is not so secure. Choose DH1 or DH2 from the drop-down list box to enable PFS. 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 (more secure, yet slower). Back Click Back to return to the previous screen. Apply Click Apply to save your changes back to the ZyXEL Device and return to the VPN-IKE screen. Cancel Click Cancel to return to the VPN-IKE screen without saving your changes. 17.14 Manual Key Setup Manual key management is useful if you have problems with IKE key management. 17.14.1 Security Parameter Index (SPI) An SPI is used to distinguish different SAs terminating at the same destination and using the same IPSec protocol. This data allows for the multiplexing of SAs to a single gateway. The SPI (Security Parameter Index) along with a destination IP address uniquely identify a particular Security Association (SA). The SPI is transmitted from the remote VPN gateway to the local VPN gateway. The local VPN gateway then uses the network, encryption and key values that the administrator associated with the SPI to establish the tunnel. Current ZyXEL implementation assumes identical outgoing and incoming SPIs. 17.15 Configuring Manual Key You only configure VPN Manual Key when you select Manual in the IPSec Key Mode field on the VPN IKE screen. This is the VPN Manual Key screen as shown next. Chapter 17 VPN Screens 239