Chapter 12 VPN
P-792H v2 User’s Guide
166
Phase 1
Negotiation
Mode
Select Main or Aggressive from the drop-down list box. Multiple SAs
connecting through a secure gateway must have the same negotiation
mode.
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.
Encryption
Algorithm
Select DES, 3DES or AES from the drop-down list box.
When you use one of these encryption algorithms for data
communications, both the sending device and the receiving device
must use the same secret key, which can be used to encrypt and
decrypt the message or to generate and verify a message
authentication code. The DES encryption algorithm uses a 56-bit key.
Triple DES (3DES) is a variation on DES that uses a 168-bit key. As a
result, 3DES is more secure than DES. It also requires more
processing power, resulting in increased latency and decreased
throughput. This implementation of AES uses a 128-bit key. AES is
faster than 3DES.
Authentication
Algorithm
Select SHA1 or MD5 from the drop-down list box. MD5 (Message
Digest 5) and SHA1 (Secure Hash Algorithm) are hash algorithms
used to authenticate packet data. The SHA1 algorithm is generally
considered stronger than MD5, but is slower. Select MD5 for minimal
security and SHA-1 for maximum security.
SA Life Time
(Seconds)
Define the length of time before an IPSec SA automatically
renegotiates in this field. 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.
Key Group You must choose a key group for phase 1 IKE setup. DH1 (default)
refers to Diffie-Hellman Group 1 a 768 bit random number. DH2 refers
to Diffie-Hellman Group 2 a 1024 bit (1Kb) random number.
Phase 2
Active Protocol Use the drop-down list box to choose from ESP or AH.
Table 45 Security > VPN > Setup > Edit > Advanced Setup (continued)
LABEL DESCRIPTION
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