Cisco RV042G - Appendix E: Ipsec NAT Traversal; Overview

E
Cisco Small Business RV0xx Series Routers Administration Guide 183
IPSec NAT Traversal
Overview
Network Address Translation (NAT) traversal is a technique developed so that
data protected by IPSec can pass through a NAT. Since IPSec provides integrity
for the entire IP datagram, any changes to the IP addressing will invalidate the
data. To resolve this issue, NAT traversal appends a new IP and UDP header to the
incoming datagram, ensuring that no changes are made to the incoming datagram
stream.
In the following scenario, Router A initiates IKE negotiation, while Router B is the
responder.
RV016
RV042 RV016
RV042
199787
WAN: 192.168.11.101
Router A - Initiator
LAN: 192.168.1.0/24
WAN: 192.168.111.101
NAT 1
LAN: 192.168.11.1
WAN: 192.168.99.11
NAT 2
LAN: 192.168.111.1
WAN: 192.168.99.22
Router B - Responder
LAN: 192.168.2.0/24
192.168.1.101
192.168.2.100