P-661H/HW Series User’s Guide
200
Chapter 12 Introduction to IPSec
Figure 119
Transport and Tunnel Mode IPSec Encapsulation
12.3.1 Transport Mode
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).
With
ESP,
protection is applied only to the upper layer protocols contained in the packet. The
IP header information and options are not used in the authentication process. Therefore, the
originating IP address cannot be verified for integrity against the data.
With the use of
AH
as the security protocol, protection is extended forward into the IP header
to verify the integrity of the entire packet by use of portions of the original IP header in the
hashing process.
12.3.2 Tunnel Mode
Tunnel
mode encapsulates the entire IP packet to transmit it securely. A
Tunnel
mode is
required for gateway services to provide access to internal systems.
Tunnel
mode is
fundamentally an IP tunnel with authentication and encryption. This is the most common
mode of operation.
Tunnel
mode is required for gateway to gateway and host to gateway
communications.
Tunnel
mode communications have two sets of IP headers:
•
Outside header
: The outside IP header contains the destination IP address of the VPN
gateway.
•
Inside header
: The inside IP header contains the destination IP address of the final
system behind the VPN gateway. The security protocol appears after the outer IP header
and before the inside IP header.
12.4 IPSec and NAT
Read this section if you are running IPSec on a host computer behind the ZyXEL Device.
Summary of Contents for P-661H Series
Page 2: ......
Page 5: ...P 661H HW Series User s Guide Certifications 5...
Page 10: ...P 661H HW Series User s Guide 10 Customer Support...
Page 44: ...P 661H HW Series User s Guide 44 Chapter 1 Getting To Know Your ZyXEL Device...
Page 76: ...P 661H HW Series User s Guide 76 Chapter 3 Wizards...
Page 108: ...P 661H HW Series User s Guide 108 Chapter 5 LAN Setup...
Page 132: ...P 661H HW Series User s Guide 132 Chapter 6 Wireless LAN...
Page 192: ...P 661H HW Series User s Guide 192 Chapter 10 Trend Micro Security Services...
Page 196: ...P 661H HW Series User s Guide 196 Chapter 11 Content Filtering...
Page 202: ...P 661H HW Series User s Guide 202 Chapter 12 Introduction to IPSec...
Page 230: ...P 661H HW Series User s Guide 230 Chapter 13 VPN Screens...
Page 234: ...P 661H HW Series User s Guide 234 Chapter 14 Static Route...
Page 246: ...P 661H HW Series User s Guide 246 Chapter 15 Bandwidth Management...
Page 250: ...P 661H HW Series User s Guide 250 Chapter 16 Dynamic DNS Setup...
Page 280: ...P 661H HW Series User s Guide 280 Chapter 19 System...
Page 290: ...P 661H HW Series User s Guide 290 Chapter 21 Tools...
Page 296: ...P 661H HW Series User s Guide 296 Chapter 23 Troubleshooting...
Page 300: ...P 661H HW Series User s Guide 300 Appendix A...
Page 304: ...P 661H HW Series User s Guide 304 Appendix C...
Page 326: ...P 661H HW Series User s Guide 326 Appendix E...
Page 328: ...P 661H HW Series User s Guide 328 Appendix F...
Page 334: ...P 661H HW Series User s Guide 334 Appendix G...
Page 368: ...P 661H HW Series User s Guide 368 Appendix K...
Page 376: ...P 661H HW Series User s Guide 376 Figure 219 Java Sun...