Chapter 18 VPN Screens
Table 110 Advanced VPN Policies
LABEL | DESCRIPTION |
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. |
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Encapsulation | Select Tunnel mode or Transport mode from the |
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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 |
| Group 1 a 768 bit random number. DH2 refers to |
| bit (1Kb) random number (more secure, yet slower). |
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Back | Click Back to return to the previous screen. |
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Apply | Click Apply to save your changes back to the ZyXEL Device and return to the |
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Cancel | Click Cancel to return to the |
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18.14 Manual Key Setup
Manual key management is useful if you have problems with IKE key management.
18.14.1 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.
18.15 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.
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