Chapter 13 VPN
LTE6100 User’s Guide
96
NAT is not normally compatible with ESP in transport mode either, but the LTE Device’s NAT
Traversal feature provides a way to handle this. NAT traversal allows you to set up an IKE SA when
there are NAT routers between the two IPSec routers.
Figure 54
NAT Router Between IPSec Routers
Normally you cannot set up an IKE SA with a NAT router between the two IPSec routers because
the NAT router changes the header of the IPSec packet. NAT traversal solves the problem by adding
a UDP port 500 header to the IPSec packet. The NAT router forwards the IPSec packet with the UDP
port 500 header unchanged. In the above figure, when IPSec router A tries to establish an IKE SA,
IPSec router B checks the UDP port 500 header, and IPSec routers A and B build the IKE SA.
For NAT traversal to work, you must:
• Use ESP security protocol (in either transport or tunnel mode).
• Use IKE keying mode.
• Enable NAT traversal on both IPSec endpoints.
• Set the NAT router to forward UDP port 500 to IPSec router A.
Finally, NAT is compatible with ESP in tunnel mode because integrity checks are performed over the
combination of the "original header plus original payload," 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 LTE Device if you enable NAT traversal.
13.3.7 ID Type and Content
With aggressive negotiation mode (see
), the LTE Device identifies
incoming SAs by ID type and content since this identifying information is not encrypted. This
enables the LTE Device to distinguish between multiple rules for SAs that connect from remote
IPSec routers that have dynamic WAN IP addresses.
Regardless of the ID type and content configuration, the LTE Device does not allow you to save
multiple active rules with overlapping local and remote IP addresses.
With main mode (see
), the ID type and content are encrypted to provide
identity protection. In this case the LTE Device can distinguish between different incoming SAs that
connect from remote IPSec routers that have dynamic WAN IP addresses. The LTE Device can
Table 40
VPN and NAT
SECURITY PROTOCOL
MODE
NAT
AH
Transport
N
AH
Tunnel
N
ESP
Transport
Y*
ESP
Tunnel
Y
A
B
Summary of Contents for LTE6100
Page 4: ...Contents Overview LTE6100 User s Guide 4...
Page 11: ...11 PART I User s Guide...
Page 12: ...12...
Page 16: ...Chapter 1 Introduction LTE6100 User s Guide 16...
Page 24: ...24...
Page 30: ...Chapter 3 Connection Status and System Info LTE6100 User s Guide 30...
Page 38: ...Chapter 4 Broadband LTE6100 User s Guide 38...
Page 48: ...Chapter 6 Routing LTE6100 User s Guide 48...
Page 66: ...Chapter 8 Network Address Translation NAT LTE6100 User s Guide 66...
Page 78: ...Chapter 10 Firewall LTE6100 User s Guide 78...
Page 84: ...Chapter 12 Parental Control LTE6100 User s Guide 84...
Page 104: ...Chapter 15 Traffic Status LTE6100 User s Guide 104...
Page 106: ...Chapter 16 User Account LTE6100 User s Guide 106...
Page 120: ...Chapter 22 Backup Restore LTE6100 User s Guide 120...
Page 122: ...Chapter 23 Diagnostic LTE6100 User s Guide 122...
Page 166: ...Appendix B Setting Up Your Computer s IP Address LTE6100 User s Guide 166...
Page 176: ...Appendix C Pop up Windows JavaScript and Java Permissions LTE6100 User s Guide 176...
Page 180: ...Appendix D Common Services LTE6100 User s Guide 180...
Page 184: ...Appendix E Legal Information LTE6100 User s Guide 184...
Page 188: ...Index LTE6100 User s Guide 188...
Page 189: ...Index LTE6100 User s Guide 189...