Chapter 25 IPSec VPN
ZyWALL USG 300 User’s Guide
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These modes are illustrated below.
In tunnel mode, the ZyWALL uses the active protocol to encapsulate the entire IP
packet. As a result, there are two IP headers:
• Outside header: The outside IP header contains the IP address of the ZyWALL or
remote IPSec router, whichever is the destination.
• Inside header: The inside IP header contains the IP address of the computer
behind the ZyWALL or remote IPSec router. The header for the active protocol
(AH or ESP) appears between the IP headers.
In transport mode, the encapsulation depends on the active protocol. With AH, the
ZyWALL includes part of the original IP header when it encapsulates the packet.
With ESP, however, the ZyWALL does not include the IP header when it
encapsulates the packet, so it is not possible to verify the integrity of the source IP
address.
IPSec SA Proposal and Perfect Forward Secrecy
An IPSec SA proposal is similar to an IKE SA proposal (see
), except that you also have the choice whether or not the ZyWALL and
remote IPSec router perform a new DH key exchange every time an IPSec SA is
established. This is called Perfect Forward Secrecy (PFS).
If you enable PFS, the ZyWALL and remote IPSec router perform a DH key
exchange every time an IPSec SA is established, changing the root key from which
encryption keys are generated. As a result, if one encryption key is compromised,
other encryption keys remain secure.
If you do not enable PFS, the ZyWALL and remote IPSec router use the same root
key that was generated when the IKE SA was established to generate encryption
keys.
The DH key exchange is time-consuming and may be unnecessary for data that
does not require such security.
Figure 367
VPN: Transport and Tunnel Mode Encapsulation
Original Packet
IP Header TCP
Header
Data
Transport Mode Packet
IP Header AH/ESP
Header
TCP
Header
Data
Tunnel Mode Packet
IP Header AH/ESP
Header
IP Header TCP
Header
Data
Summary of Contents for Unified Security Gateway ZyWALL 300
Page 2: ......
Page 30: ...Table of Contents ZyWALL USG 300 User s Guide 30 ...
Page 31: ...31 PART I User s Guide ...
Page 32: ...32 ...
Page 38: ...Chapter 1 Introducing the ZyWALL ZyWALL USG 300 User s Guide 38 ...
Page 46: ...Chapter 2 Features and Applications ZyWALL USG 300 User s Guide 46 ...
Page 64: ...Chapter 3 Web Configurator ZyWALL USG 300 User s Guide 64 ...
Page 74: ...Chapter 4 Installation Setup Wizard ZyWALL USG 300 User s Guide 74 ...
Page 116: ...Chapter 6 Configuration Basics ZyWALL USG 300 User s Guide 116 ...
Page 184: ...Chapter 7 Tutorials ZyWALL USG 300 User s Guide 184 ...
Page 221: ...221 PART II Technical Reference ...
Page 222: ...222 ...
Page 288: ...Chapter 11 Registration ZyWALL USG 300 User s Guide 288 ...
Page 378: ...Chapter 14 Trunks ZyWALL USG 300 User s Guide 378 ...
Page 394: ...Chapter 15 Policy and Static Routes ZyWALL USG 300 User s Guide 394 ...
Page 408: ...Chapter 16 Routing Protocols ZyWALL USG 300 User s Guide 408 ...
Page 428: ...Chapter 19 NAT ZyWALL USG 300 User s Guide 428 ...
Page 454: ...Chapter 23 Authentication Policy ZyWALL USG 300 User s Guide 454 ...
Page 472: ...Chapter 24 Firewall ZyWALL USG 300 User s Guide 472 ...
Page 534: ...Chapter 27 SSL User Screens ZyWALL USG 300 User s Guide 534 ...
Page 536: ...Chapter 28 SSL User Application Screens ZyWALL USG 300 User s Guide 536 ...
Page 544: ...Chapter 29 SSL User File Sharing ZyWALL USG 300 User s Guide 544 ...
Page 638: ...Chapter 35 ADP ZyWALL USG 300 User s Guide 638 Figure 448 Profiles Protocol Anomaly ...
Page 682: ...Chapter 37 Content Filter Reports ZyWALL USG 300 User s Guide 682 ...
Page 700: ...Chapter 38 Anti Spam ZyWALL USG 300 User s Guide 700 ...
Page 722: ...Chapter 39 Device HA ZyWALL USG 300 User s Guide 722 ...
Page 738: ...Chapter 40 User Group ZyWALL USG 300 User s Guide 738 ...
Page 744: ...Chapter 41 Addresses ZyWALL USG 300 User s Guide 744 ...
Page 756: ...Chapter 43 Schedules ZyWALL USG 300 User s Guide 756 ...
Page 772: ...Chapter 45 Authentication Method ZyWALL USG 300 User s Guide 772 ...
Page 794: ...Chapter 46 Certificates ZyWALL USG 300 User s Guide 794 ...
Page 806: ...Chapter 48 SSL Application ZyWALL USG 300 User s Guide 806 ...
Page 811: ...Chapter 49 Endpoint Security ZyWALL USG 300 User s Guide 811 ...
Page 866: ...Chapter 50 System ZyWALL USG 300 User s Guide 866 ...
Page 873: ...Chapter 51 Log and Report ZyWALL USG 300 User s Guide 873 ...
Page 886: ...Chapter 51 Log and Report ZyWALL USG 300 User s Guide 886 ...
Page 916: ...Chapter 54 Packet Flow Explore ZyWALL USG 300 User s Guide 916 ...
Page 918: ...Chapter 55 Reboot ZyWALL USG 300 User s Guide 918 ...
Page 920: ...Chapter 56 Shutdown ZyWALL USG 300 User s Guide 920 ...
Page 948: ...Chapter 58 Product Specifications ZyWALL USG 300 User s Guide 948 ...
Page 1014: ...Appendix A Log Descriptions ZyWALL USG 300 User s Guide 1014 ...
Page 1124: ...Appendix F Open Software Announcements ZyWALL USG 300 User s Guide 1124 ...