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How does TCP work with NAT?
An internal endpoint initiates a TCP connection through a NAT by sending a SYN packet. The NAT allocates (or reuses) a mapping for the connection, as described in the previous section. The mapping defines the external IP address and port used for translation of all packets for that connection.
What is EIM NAT?
An Endpoint-Independent Mapping NAT (EIM-NAT, for short) is a NAT device employing Endpoint-Independent Mapping. An EIM-NAT can have any type of filtering behavior.
How does NAT traversal works?
Network Address Translation-Traversal (NAT-T) is a method for getting around IP address translation issues encountered when data protected by IPsec passes through a NAT device for address translation. NAT-T encapsulates both IKE and ESP traffic within UDP with port 4500 used as both the source and destination port.
What is endpoint independent filtering?
In “Endpoint-Independent Filtering”, the Endpoint refers to an External Endpoint. “Endpoint-Independent Filtering” checks only the i) destination IP and ii) destination port of an inbound packet sent by an External Endpoint to decide whether to pass the packet or not.
What is Endpoint independent mapping?
Endpoint independent mapping (EIM) ensures the assignment of the same external address and port for all connections from a given host if they use the same internal port. This means if they come from a different source port, you are free to assign a different external address.
Why is Nat-T used?
How does nat work with incoming UDP packets from unknown?
My understanding of NAT is that UDP packets going out from the client to a specific endpoint will result in a temporary entry into the NAT table mapping the source port to the destination endpoint. (Is this right?)
What happens when a client is behind a NAT?
Using the original variant of the file transfer protocol (FTP) the client establishes a TCP connection to the server and then the server establishes a second TCP connection back to the client. This typically will not work when the client is behind a NAT.
How is Network Address Translation ( NAT ) used in SIP?
A. The NAT support for voice feature allows SIP embedded messages passing through a router configured with Network Address Translation (NAT) to be translated back to the packet. An application layer gateway (ALG) is used with NAT to translate the voice packets.
How are UDP ports different from TCP ports?
As jonathanjo points out, a UDP NAPT table entry will consist of more than just a UDP port number (with NAPT, there are separate tables for UDP, TCP, and ICMP, and UDP port 12345 is different than TCP port 12345, while ICMP doesn’t use ports but uses a Query ID instead of port number).