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P-334U/P-335U User’s Guide
Chapter 13 IPSec VPN 159
13.6 IPSec SA Using Manual Keys
You might set up an IPSec SA using manual keys when you want to establish a VPN tunnel
quickly, for example, for troubleshooting. You should only do this as a temporary solution,
however, because it is not as secure as a regular IPSec SA.
In IPSec SAs using manual keys, the ZyXEL Device and remote IPSec router do not establish
an IKE SA. They only establish an IPSec SA. As a result, an IPSec SA using manual keys has
some characteristics of IKE SA and some characteristics of IPSec SA. There are also some
differences between IPSec SA using manual keys and other types of SA.
IPSec Protocol Select the security protocols used for an SA.
Both AH and ESP increase processing requirements and communications
latency (delay).
If you select ESP here, you must select options from the Encryption Algorithm
and Authentication Algorithm fields (described below).
Encryption Algorithm Select which key size and encryption algorithm to use in the IKE SA. Choices
are:
DES - a 56-bit key with the DES encryption algorithm
3DES - a 168-bit key with the DES encryption algorithm
The ZyXEL Device and the remote IPSec router must use the same algorithms
and keys. Longer keys require more processing power, resulting in increased
latency and decreased throughput.
Authentication
Algorithm
Select which hash algorithm to use to authenticate packet data in the IPSec SA.
Choices are SHA1 and MD5. SHA1 is generally considered stronger than MD5,
but it is also slower.
SA Life Time Define the length of time before an IPSec SA automatically renegotiates in this
field. The minimum value is 180 seconds.
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.
Perfect Forward
Secret (PFS)
Select whether or not you want to enable Perfect Forward Secrecy (PFS) and, if
you do, which Diffie-Hellman key group to use for encryption. Choices are:
None - disable PFS
DH1 - enable PFS and use a 768-bit random number
DH2 - enable PFS and use a 1024-bit random number
PFS changes the root key that is used to generate encryption keys for each
IPSec SA. It is more secure but takes more time.
Basic... Click Basic... to go to the previous VPN configuration screen.
Apply Click Apply to save the changes.
Reset Click Reset to begin configuring this screen afresh.
Table 53 Security > VPN > Rule Setup: IKE (Advanced) (continued)
LABEL DESCRIPTION