ZyXEL Communications ZyWall USG20-VPN User Manual page 343

Table 135 Configuration > VPN > IPSec VPN > VPN Connection > Edit (continued)
LABEL DESCRIPTION
Proposal Use this section to manage the encryption algorithm and authentication algorithm
pairs the USG accepts from the remote IPSec router for negotiating the IPSec SA.
Add Click this to create a new entry.
Edit Select an entry and click this to be able to modify it.
Remove Select an entry and click this to delete it.
# This field is a sequential value, and it is not associated with a specific proposal. The
sequence of proposals should not affect performance significantly.
Encryption This field is applicable when the Active Protocol is ESP. Select which key size and
encryption algorithm to use in the IPSec SA. Choices are:
NULL - no encryption key or algorithm
DES - a 56-bit key with the DES encryption algorithm
3DES - a 168-bit key with the DES encryption algorithm
AES128 - a 128-bit key with the AES encryption algorithm
AES192 - a 192-bit key with the AES encryption algorithm
AES256 - a 256-bit key with the AES encryption algorithm
The USG and the remote IPSec router must both have at least one proposal that uses
use the same encryption and the same key.
Longer keys are more secure, but require more processing power, resulting in
increased latency and decreased throughput.
Authentication Select which hash algorithm to use to authenticate packet data in the IPSec SA.
Choices are SHA1, SHA256, SHA512 and MD5. SHA is generally considered
stronger than MD5, but it is also slower.
The USG and the remote IPSec router must both have a proposal that uses the same
authentication algorithm.
Perfect Forward Select whether or not you want to enable Perfect Forward Secrecy (PFS) and, if you
Secrecy (PFS)
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
DH5 - enable PFS and use a 1536-bit random number
PFS changes the root key that is used to generate encryption keys for each IPSec SA.
The longer the key, the more secure the encryption, but also the longer it takes to
encrypt and decrypt information. Both routers must use the same DH key group.
PFS is ignored in initial IKEv2 authentication but is used when reauthenticating.
Related Settings
Zone Select the security zone into which to add this VPN connection policy. Any security
rules or settings configured for the selected zone apply to this VPN connection policy.
Connectivity Check The USG can regularly check the VPN connection to the gateway you specified to
make sure it is still available.
Enable Select this to turn on the VPN connection check.
Connectivity Check
Chapter 21 IPSec VPN
USG20(W)-VPN Series User's Guide
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