Chapter 16 VPN
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which is unchanged by a NAT device. The compatibility of AH and ESP with NAT in
tunnel and transport modes is summarized in the following table.
Y* - This is supported in the ZyXEL Device if you enable NAT traversal.
16.6.4 Encapsulation
The two modes of operation for IPSec VPNs are Transport mode and Tunnel
mode.
Figure 103
Transport and Tunnel Mode IPSec Encapsulation
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.
Table 62
VPN and NAT
SECURITY
PROTOCOL
MODE
NAT
AH
Transport
N
AH
Tunnel
N
ESP
Transport
Y*
ESP
Tunnel
Y
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Страница 8: ...Safety Warnings P 661HNU Fx User s Guide 8...
Страница 10: ...Contents Overview P 661HNU Fx User s Guide 10...
Страница 18: ...Table of Contents P 661HNU Fx User s Guide 18 Appendix G Legal Information 393 Index 1...
Страница 19: ...19 PART I User s Guide...
Страница 20: ...20...
Страница 28: ...Chapter 1 Introduction P 661HNU Fx User s Guide 28...
Страница 36: ...Chapter 2 Introducing the Web Configurator P 661HNU Fx User s Guide 36...
Страница 79: ...79 PART II Technical Reference...
Страница 80: ...80...
Страница 86: ...Chapter 4 Connection Status and System Info Screens P 661HNU Fx User s Guide 86...
Страница 140: ...Chapter 6 Wireless P 661HNU Fx User s Guide 140...
Страница 172: ...Chapter 8 Routing P 661HNU Fx User s Guide 172...
Страница 176: ...Chapter 9 DNS Route P 661HNU Fx User s Guide 176...
Страница 260: ...Chapter 24 Backup Restore P 661HNU Fx User s Guide 260...
Страница 281: ...Chapter 27 Product Specifications P 661HNU Fx User s Guide 281...
Страница 282: ...Chapter 27 Product Specifications P 661HNU Fx User s Guide 282...
Страница 334: ...Appendix C Pop up Windows Java Script and Java Permissions P 661HNU Fx User s Guide 334...
Страница 358: ...Appendix D Wireless LANs P 661HNU Fx User s Guide 358...
Страница 392: ...Appendix F Open Software Announcements P 661HNU Fx User s Guide 392...
Страница 403: ...Index P 661HNU Fx User s Guide 403...
Страница 404: ...Index P 661HNU Fx User s Guide 404...