Manual Key Setup; Security Parameter Index (Spi) - ZyXEL Communications P-2612HW Series User Manual

14.5 Manual Key Setup

Manual key management is useful if you have problems with IKE key
management.

14.5.1 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.
P-2612HW Series User's Guide
Chapter 14 VPN
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