Chapter 4
Advanced Configuration
48
10/100 8-Port VPN Router
Perfect Forward Secrecy
If the Perfect Forward Secrecy
(PFS) feature is enabled, IKE Phase 2 negotiation will
generate new key material for IP traffic encryption and
authentication, so hackers using brute force to break
encryption keys will not be able to obtain future IPSec
keys.
Phase 2 DH Group
If the Perfect Forward Secrecy feature
is disabled, then no new keys will be generated, so you do
not need to set the Phase 2 DH Group (the key for Phase 2
will match the key in Phase 1).
There are three groups of different prime key lengths.
Group 1 is 768 bits, and Group 2 is 1,024 bits. Group 5 is
1,536 bits. If network speed is preferred, select
Group 1
.
If network security is preferred, select
Group 5
. You do
not have to use the same DH Group that you used for
Phase 1.
Phase 2 Encryption
Phase 2 is used to create one or
more IPSec SAs, which are then used to key IPSec sessions.
Select a method of encryption:
NULL
,
DES
(56-bit),
3DES
(168-bit),
AES-128
(128-bit),
AES-192
(192-bit), or
AES-256
(256-bit). It determines the length of the key used to
encrypt or decrypt ESP packets. AES-256 is recommended
because it is more secure. Both ends of the VPN tunnel
must use the same Phase 2 Encryption setting.
Phase 2 Authentication
Select a method of
authentication,
NULL
,
MD5
, or
SHA
. The authentication
method determines how the ESP packets are validated.
MD5 is a one-way hashing algorithm that produces a
128-bit digest. SHA is a one-way hashing algorithm that
produces a 160-bit digest. SHA is recommended because
it is more secure. Both ends of the VPN tunnel must use
the same Phase 2 Authentication setting.
Phase 2 SA Life Time
Configure the length of time a VPN
tunnel is active in Phase 2. The default is
3600
seconds.
Preshared Key
This specifies the pre-shared key used
to authenticate the remote IKE peer. Enter a key of
keyboard and hexadecimal characters, e.g., My_@123
or 4d795f40313233. This field allows a maximum of 30
characters and/or hexadecimal values. Both ends of
the VPN tunnel must use the same Preshared Key. It is
strongly recommended that you change the Preshared
Key periodically to maximize VPN security.
Manual
If you select Manual, you generate the key yourself, and
no key negotiation is needed. Manual key management is
used in small static environments or for troubleshooting
purposes.
Keying Mode > Manual (Tunnel Only)
Incoming and Outgoing SPI (Security Parameter
Index)
SPI is carried in the ESP (Encapsulating Security
Payload Protocol) header and enables the receiver and
sender to select the SA, under which a packet should be
processed. Hexadecimal values is acceptable, and the
valid range is 100~ffffffff. Each tunnel must have a unique
Incoming SPI and Outgoing SPI. No two tunnels share the
same SPI. The Incoming SPI here must match the Outgoing
SPI value at the other end of the tunnel, and vice versa.
Encryption
Select a method of encryption,
DES
or
3DES
.
This determines the length of the key used to encrypt or
decrypt ESP packets. DES is 56-bit encryption and 3DES
is 168-bit encryption. 3DES is recommended because it is
more secure. Make sure both ends of the VPN tunnel use
the same encryption method.
Authentication
Select a method of authentication,
MD5
or
SHA1
. The Authentication method determines how
the ESP packets are validated. MD5 is a one-way hashing
algorithm that produces a 128-bit digest. SHA is a one-way
hashing algorithm that produces a 160-bit digest. SHA1
is recommended because it is more secure. Make sure
both ends of the VPN tunnel use the same authentication
method.
Encryption Key
This field specifies a key used to encrypt
and decrypt IP traffic. Enter a key of hexadecimal values.
If DES is selected, the Encryption Key is 16-bit, which
requires 16 hexadecimal values. If you do not enter enough
hexadecimal values, then the rest of the Encryption
Key will be automatically completed with zeroes, so the
Encryption Key will be 16-bit. If 3DES is selected, the
Encryption Key is 48-bit, which requires 40 hexadecimal
values. If you do not enter enough hexadecimal values,
then the rest of the Encryption Key will be automatically
completed with zeroes, so the Encryption Key will be
48-bit. Make sure both ends of the VPN tunnel use the
same Encryption Key.
Authentication Key
This field specifies a key used to
authenticate IP traffic. Enter a key of hexadecimal values.
If MD5 is selected, the Authentication Key is 32-bit, which
requires 32 hexadecimal values. If you do not enter enough
hexadecimal values, then the rest of the Authentication Key
will be automatically completed with zeroes until it has 32
hexadecimal values. If SHA is selected, the Authentication
Key is 40-bit, which requires 40 hexadecimal values. If you
do not enter enough hexadecimal values, then the rest of