VPN ON THE CISCO ASA: NAT Traversal - Intense School

Figure 1: Standard IPsec Tunnel Through a NAT/PAT Point (No UDP Encapsulation) Figure 2: IPsec Packet with UDP Encapsulation IPsec Data Plane Configuration Guide, Cisco IOS Release 15M&T 4 IPsec NAT Transparency Feature Design of IPsec NAT Traversal NAT Traversal (NAT-T) Security Issues | Computerworld NAT-T is designed to solve the problems inherent in using IPSec with NAT. NAT-T adds a UDP header that encapsulates the ESP header (it sits between the ESP header and the outer IP header). Application Layer Gateway for IPSec Protocol NAT-Traversal (NAT-T) capable IPSec endpoints detect the presence of an intermediate NAT device during IKE phase 1 and switch to UDP port 4500 for all subsequent IKE and ESP traffic (encapsulating ESP in UDP). Without NAT-T support on the peer IPSec endpoints, IPSec protected ESP traffic is transmitted without any UDP encapsulation. Problems due to widespread use of NAT and IPSEC considerations

ike 1:YARD_0:965: send IPsec SA delete, spi 95d5b0d1 About NAT Traversal: The Network Address Translation (NAT) is a way to convert private IP addresses to publicly routable internet addresses and vise versa. When an IP packet passes through a NAT device, the source or destination address in the IP header is modified.

EC2 VPC VPN Update – NAT Traversal, Additional Encryption Oct 28, 2015 Site-to-site IPSec VPN through NAT - Packet Pushers May 03, 2017

11. Remote Access and the Importance of Nat-T with IPSec

IPsec NAT-Traversal. NAT-T (NAT traversal or UDP encapsulation) makes sure that IPsec VPN connections stay open when traffic goes through gateways or devices that use NAT. When an IP packet passes through a network address translator device, it is changed in a way that is not compatible with IPsec. IPsec NAT Transparency - Cisco Figure 1: Standard IPsec Tunnel Through a NAT/PAT Point (No UDP Encapsulation) Figure 2: IPsec Packet with UDP Encapsulation IPsec Data Plane Configuration Guide, Cisco IOS Release 15M&T 4 IPsec NAT Transparency Feature Design of IPsec NAT Traversal NAT Traversal (NAT-T) Security Issues | Computerworld NAT-T is designed to solve the problems inherent in using IPSec with NAT. NAT-T adds a UDP header that encapsulates the ESP header (it sits between the ESP header and the outer IP header). Application Layer Gateway for IPSec Protocol NAT-Traversal (NAT-T) capable IPSec endpoints detect the presence of an intermediate NAT device during IKE phase 1 and switch to UDP port 4500 for all subsequent IKE and ESP traffic (encapsulating ESP in UDP). Without NAT-T support on the peer IPSec endpoints, IPSec protected ESP traffic is transmitted without any UDP encapsulation.