User's Manual

Chapter 15 IPSec VPN
NBG-460N User’s Guide
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Pre-Shared Key Type your pre-shared key in this field. A pre-shared key identifies a
communicating party during a phase 1 IKE negotiation. It is called
"pre-shared" because you have to share it with another party before
you can communicate with them over a secure connection.
Type from 8 to 31 case-sensitive ASCII characters or from 16 to 62
hexadecimal ("0-9", "A-F") characters. You must precede a
hexadecimal key with a "0x” (zero x), which is not counted as part of
the 16 to 62 character range for the key. For example, in
"0x0123456789ABCDEF", “0x” denotes that the key is hexadecimal
and “0123456789ABCDEF” is the key itself.
Both ends of the VPN tunnel must use the same pre-shared key. You
will receive a “PYLD_MALFORMED” (payload malformed) packet if the
same pre-shared key is not used on both ends.
IKE Phase 2
Encapsulation
Mode
Select Tunnel mode or Transport mode.
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 NBG-460N 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.
Table 69 Security > VPN > General > Rule Setup: IKE (Advanced) (continued)
LABEL DESCRIPTION