ZyXEL Communications P-2602 manual Manual Key Setup, Configuring Manual Key, VPN Screens 239

	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-1for 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-IKEscreen 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