PAT

PAT stands for Port Address Translation, which is a type of Network Address Translation (NAT) commonly used in computer networking to allow multiple devices within a private network to share a single public IP address. Also known as NAT Overload or NAT with Port Multiplication, PAT operates by using different port numbers to distinguish between connections originating from different devices.

In a PAT configuration, the router or firewall performing NAT assigns unique port numbers to outgoing connections from devices within the private network. This allows multiple devices to use the same public IP address simultaneously, with each device's traffic being differentiated based on the combination of the source IP address, source port, destination IP address, and destination port.

 

Key features of PAT include:

1. Port Multiplexing: PAT uses port numbers to multiplex multiple private IP addresses into a single public IP address. Each outgoing connection from a device within the private network is assigned a unique port number on the public IP address.

2. Dynamic Port Allocation: PAT dynamically assigns port numbers from a range of available ports to outgoing connections as needed. When a device initiates a connection to an external network, the router or firewall selects an available port number for that connection.

3. Translation Table: PAT maintains a translation table that maps each private IP address and port combination to the corresponding public IP address and port. This table is used to perform the translation of packet headers as traffic passes through the NAT device.

4. Conservation of Public IP Addresses: PAT conserves public IP addresses by allowing multiple devices within a private network to share a single public IP address. This helps address the shortage of IPv4 addresses and reduces the need for acquiring additional public IP addresses.

5. Enhanced Security: Like other forms of NAT, PAT provides a level of security by hiding internal IP addresses from external networks. It prevents direct inbound access to devices within the private network, reducing the risk of unauthorized access and network attacks.

 

PAT is commonly used in home and small business environments where a limited number of public IP addresses are available and multiple devices need to access the internet simultaneously. It is also used by internet service providers (ISPs) to manage IP address allocation for their customers' networks.

 

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