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Chapter 4 Wizard Setup
ZyWALL USG 300 User’s Guide
106
4.8.6.1 Phase 2 Setting
Phase 2 in an IKE uses the SA that was established in phase 1 to negotiate SAs for IPSec.
Figure 40 VPN Advanced Wizard: Step 4
The following table describes the labels in this screen.
Table 20 VPN Advanced Wizard: Step 4
LABEL DESCRIPTION
Phase 2 Setting
Active Protocol Select the security protocols used for an SA.
Both AH and ESP increase ZyWALL processing requirements and
communications latency (delay).
Encapsulation Tunnel is compatible with NAT, Transport is not.
Tunnel mode encapsulates the entire IP packet to transmit it securely. Tunnel
mode is required for gateway services to provide access to internal systems.
Tunnel mode is fundamentally an IP tunnel with authentication and encryption.
Transport mode is used to protect upper layer protocols and only affects the
data in the IP packet. In Transport mode, the IP packet contains the security
protocol (AH or ESP) located after the original IP header and options, but before
any upper layer protocols contained in the packet (such as TCP and UDP).
Encryption Algorithm When DES is used for data communications, both sender and receiver must
know 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. AES128 uses a 128-bit key and is faster than 3DES. AES192 uses
a 192-bit key and AES256 uses a 256-bit key. Select Null to have no
encryption.