ZyXEL Communications P-334 - Manual (Page 176)

Prestige 334 User’s Guide
175 Chapter 15 VPN Screens
15.13.1 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.
15.14 Configuring Manual Key
You only configure VPN Manual Key when you select Manual in the IPSec Keying Mode
field on the Rule Setup IKE screen. This is the Rule Setup Manual screen as shown next.
Note: Current ZyXEL implementation assumes identical
outgoing and incoming SPIs