Network: What is the diference between NAT and PAT?

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NAT (Network Address Translation) and PAT (Port Address Translation) are both techniques used in networking to allow multiple devices on a private network to share a single public IP address for internet communication. However, they differ in how they achieve this and the level of granularity they provide in mapping private IP addresses to public IP addresses.

  1. NAT (Network Address Translation):
    • NAT translates private IP addresses to a single public IP address. It operates at the IP address level.
    • In traditional NAT, each private IP address is mapped to a unique public IP address.
    • NAT maintains a one-to-one mapping between private IP addresses and public IP addresses.
    • NAT does not modify port numbers in the TCP/UDP headers.
    • NAT is commonly used in scenarios where a limited pool of public IP addresses is available, such as in small to medium-sized networks.
  2. PAT (Port Address Translation), also known as NAT Overload:
    • PAT translates private IP addresses to a single public IP address but uses unique port numbers to distinguish between different connections. It operates at both the IP address and port number level.
    • In PAT, multiple private IP addresses are mapped to a single public IP address, but each connection is distinguished by unique port numbers.
    • PAT maintains a many-to-one mapping between private IP addresses and public IP addresses, using different port numbers to differentiate between connections.
    • PAT modifies both the IP addresses and port numbers in the TCP/UDP headers.
    • PAT allows a much larger number of devices to share a single public IP address compared to traditional NAT, as it can multiplex connections based on port numbers.
    • PAT is commonly used in scenarios where a large number of devices need to access the internet through a single public IP address, such as in home networks, small offices, or large enterprises.

In summary, while both NAT and PAT serve the purpose of allowing multiple devices to share a single public IP address for internet communication, PAT provides a higher level of scalability and efficiency by using unique port numbers to differentiate between connections, allowing a larger number of devices to share a single public IP address.

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