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Is NAT traversal secure?
Since the header is encrypted, NAT can’t change it. This means the checksum is invalid, so the receiving computer rejects the packet. In addition, NAT isn’t able to use the port numbers in TCP and UDP headers to multiplex packets to multiple internal computers when those headers have been encrypted by ESP.
What does the IPsec transport mode do?
Transport mode, the default mode for IPSec, provides for end-to-end security. It can secure communications between a client and a server. When using the transport mode, only the IP payload is encrypted. AH or ESP provides protection for the IP payload.
Is Tunnel mode more secure than transport mode?
The key difference between transport and tunnel mode is where policy is applied. In tunnel mode, the original packet is encapsulated in another IP header. The addresses in the other header can be different. The packets can be protected by AH, ESP, or both in each mode.
Why NAT traversal is required?
Nat Traversal, also known as UDP encapsulation, allows traffic to get to the specified destination when a device does not have a public IP address. This is usually the case if your ISP is doing NAT, or the external interface of your firewall is connected to a device that has NAT enabled.
What is the difference between IPsec tunnel and transport mode?
In a quick sentence, transport mode IPsec only encapsulates the inner content excluding the original IP header, while tunnel mode encapsulates the entire inner content, including the IP header. In each case, the content needs to traverse a network, therefore the outer IP header has to come from somewhere.
What is NAT traversal mode?
Are there any security issues with NAT traversal?
Microsoft recently revealed that the way IPSec and NAT-T work can cause a security threat wherein IPSec traffic intended for one computer may be routed to the wrong computer, if certain criteria exist. For more details, see KB article 885348 .
Where did the IPSEC transport mode NAT traversal security risks originate?
By the way, the FAQ entry’s answer is based on a quote form an email by Andreas Steffen (founder of the strongSwan project) from 2009, which, unfortunately, is not available in the mailing list archives anymore. But looking at old versions of the answer in the history of the FAQ page does point to this origin.
Do you need a Cisco account for IPsec NAT transparency?
An account on Cisco.com is not required. The IPsec NAT Transparency feature introduces support for IP Security (IPsec) traffic to travel through Network Address Translation (NAT) or Port Address Translation (PAT) points in the network by addressing many known incompatibilities between NAT and IPsec.
What happens if two NAT devices use the same transport mode?
If two clients behind the same NAT device connect to the same server using Transport Mode this might result in duplicate IPsec policies (i.e. between the NAT device’s public IP and the server’s IP). This means the server may only be able to send traffic to one of the clients (usually the one that connected last).