Chapter 11 IPSec VPN
P-793H User’s Guide
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• Inside header: The inside IP header contains the IP address of the computers behind the
ZyXEL Device or remote IPSec router.
In transport mode, the IP header is the original IP header, and the encapsulation depends on
the active protocol. If the active protocol is AH, the ZyXEL Device includes part of the IP
header when it encapsulates the packet. If the active protocol is ESP, the ZyXEL Device does
not include the original IP header when it encapsulates the packet, in which case it is not
possible to verify the integrity of the source IP address.
"
The ZyXEL Device and remote IPSec router must use the same
encapsulation.
Usually, you should use tunnel mode because it is more secure. Transport mode should only
be used when the IPSec SA is used for communication between the ZyXEL Device and
remote IPSec router (for example, for remote management), not between computers on the
local and remote networks.
11.1.3.4 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 ZyXEL Device 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 ZyXEL Device and remote IPSec router perform a DH key exchange
every time an IPSec SA is established, changing the shared secret from which encryption keys
are generated. As a result, if one encryption key is compromised, other encryption keys are
secure because they are created from different shared secrets.
If you do not enable PFS, the ZyXEL Device and remote IPSec router use the same shared
secret that was generated when the IKE SA was established to generate encryption keys. The
ZyXEL Device and remote IPSec router still create a new shared secret every time they
establish (or re-establish) the IKE SA.
A DH key exchange is time-consuming. You might consider disabling PFS, if it takes a long
time to establish IPSec SA and if the VPN tunnel has good security (for example, strong
encryption) without it.
11.1.4 Additional Topics for IPSec SA
This section provides more information about IPSec SA.
11.1.4.1 IPSec SA using Manual Keys
You might set up an IPSec SA using manual keys when you want to establish a VPN tunnel
quickly (for example, while troubleshooting). You should do this only as a temporary solution,
however, because it is not as secure as a regular IPSec SA.
Summary of Contents for G.SHDSL.bis 4-port Security Gateway P-793H
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Page 7: ...Safety Warnings P 793H User s Guide 7 This product is recyclable Dispose of it properly ...
Page 8: ...Safety Warnings P 793H User s Guide 8 ...
Page 30: ...List of Figures P 793H User s Guide 30 ...
Page 36: ...List of Tables P 793H User s Guide 36 ...
Page 38: ...38 ...
Page 68: ...Chapter 4 Point to 2 point Configuration P 793H User s Guide 68 ...
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Page 114: ...Chapter 7 Network Address Translation NAT Screens P 793H User s Guide 114 ...
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Page 152: ...Chapter 10 Content Filtering P 793H User s Guide 152 ...
Page 180: ...Chapter 12 Static Route P 793H User s Guide 180 ...
Page 194: ...Chapter 14 Dynamic DNS Setup P 793H User s Guide 194 ...
Page 216: ...Chapter 16 Universal Plug and Play UPnP P 793H User s Guide 216 ...
Page 217: ...217 PART IV Maintenance System 219 Logs 225 Tools 229 Diagnostic 235 ...
Page 218: ...218 ...
Page 224: ...Chapter 17 System P 793H User s Guide 224 ...
Page 234: ...Chapter 19 Tools P 793H User s Guide 234 ...
Page 238: ...238 ...
Page 244: ...Chapter 21 Introducing the SMT P 793H User s Guide 244 ...
Page 248: ...Chapter 22 General Setup P 793H User s Guide 248 ...
Page 256: ...Chapter 23 WAN Setup P 793H User s Guide 256 ...
Page 262: ...Chapter 24 LAN Setup P 793H User s Guide 262 ...
Page 278: ...Chapter 27 Static Route Setup P 793H User s Guide 278 ...
Page 308: ...Chapter 30 Filter Configuration P 793H User s Guide 308 ...
Page 310: ...Chapter 31 SNMP Configuration P 793H User s Guide 310 ...
Page 312: ...Chapter 32 System Password P 793H User s Guide 312 ...
Page 322: ...Chapter 33 System Information Diagnosis P 793H User s Guide 322 ...
Page 352: ...Chapter 37 Schedule Setup P 793H User s Guide 352 ...
Page 360: ...360 ...
Page 366: ...Appendix B Wall mounting Instructions P 793H User s Guide 366 ...
Page 400: ...Appendix F IP Address Assignment Conflicts P 793H User s Guide 400 ...
Page 404: ...Appendix G Common Services P 793H User s Guide 404 ...
Page 432: ...Appendix K Legal Information P 793H User s Guide 432 ...
Page 443: ...Index P 793H User s Guide 443 ...
Page 444: ...Index P 793H User s Guide 444 ...