Prestige 652H/HW Series User’s Guide
Introduction to IPSec
15-5
match. The VPN device at the receiving end doesn't know about the NAT in the middle, so it assumes that
the data has been maliciously altered.
IPSec using
ESP
in
Tunnel
mode encapsulates the entire original packet (including headers) in a new IP
packet. The new IP packet's source address is the outbound address of the sending VPN gateway, and its
destination address is the inbound address of the VPN device at the receiving end. When using
ESP
protocol
with authentication, the packet contents (in this case, the entire original packet) are encrypted. The encrypted
contents, but not the new headers, are signed with a hash value appended to the packet.
Tunnel
mode
ESP
with authentication is compatible with NAT because integrity checks are performed over
the combination of the "original header plus original payload," which is unchanged by a NAT device.
Transport
mode
ESP
with authentication is not compatible with NAT, although NAT traversal provides a
way to use
Transport
mode
ESP
when there is a NAT router between the IPSec endpoints (see
section 16.7
for details).
Table 15-1 VPN and NAT
SECURITY PROTOCOL
MODE
NAT
AH Transport
N
AH Tunnel
N
ESP Transport
N
ESP Tunnel
Y
Summary of Contents for Prestige 652H series
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Page 120: ...Prestige 652H HW Series User s Guide 8 12 WAN Setup Figure 8 6 Advanced WAN Backup ...
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Page 227: ...Prestige 652H HW Series User s Guide VPN Screens 16 23 Figure 16 8 Manual Setup ...
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