Why NAT traversal is used in IPsec?

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.

What is enable NAT traversal?

NAT Traversal, if enabled, automatically detects if network address translation (NAT) is being performed between the two VPN tunnel endpoints, since this “in-between” NAT can interfere with IPsec/ESP traffic also, some routers that may exist between the VPN peers might be programmed to block IPsec pass-through, or have …

What is VPN NAT traversal?

NAT traversal (NAT-T) prevents intermediary devices from applying NAT to VPN communications if NAT is found to prevent the communications from working. NAT traversal encapsulates the IKE and IPsec communications inside UDP packets. The NAT-T encapsulation option does not affect mobile VPNs.

Why does IPSec use port 4500?

Therefore, to allow that traffic to pass thru NAT, according to the defined standards, every device should allow & process UDP4500 if NAT-T is detected, & the esp/ah packet is re-encapsulated with the port UDP4500, allowing the esp/ah inside traffic to successfully pass thru tunnel as well as thru NAT, so encryption ( …

What is NAT traversal in VPN Fortigate?

Network Address Translation (NAT) is a way to convert private IP addresses to publicly routable Internet addresses and vice versa. When the Nat-traversal option is enabled, outbound encrypted packets are wrapped inside a UDP IP header that contains a port number.

How do I disable NAT traversal?

Navigate to Manage | Connectivity | VPN | Advance settings | Enable/Disable NAT traversal. By default in all SonicOS, NAT traversal will be enabled.

Why does IPsec use port 4500?

What port is 4500?

Service Name and Transport Protocol Port Number Registry

Service Name	Port Number	Description
ipsec-nat-t	4500	IPsec NAT-Traversal
ipsec-nat-t	4500	IPsec NAT-Traversal
xpra	14500	xpra network protocol
	14500	Reserved

Should I open port 500?

UDP Port 500 should be opened to allow Internet Security Association and Key Management Protocol (ISAKMP) traffic to be forwarded through your firewalls.