This video shows how to configure port forwarding on a BT Home Hub. Regardless of exactly how you configure it, as it varies by device, what you are essentially doing is creating a mapping table that maps an external address and port to an internal address and port. This site has a comprehensive guide covering 100s of routers, and also port lists for many of the games/applications. To configure port forwarding on your router you will need Admin privileges. Internet) and forwarded to the internal network. This step is important as the forwarding will be set to send packets to a specific internal IP address.ĭepending on your Application you may need a list of ports that need to be available from the the external network (i.e. Video Internal and external IP addressesĮnabling Port forwarding and Checking Open Portsīefore you set up port forwarding you ideally will need to configure a static IP address for the Internal device.To do this you statically map the external IP address + port 80 to the Internal IP address of the web server + port 80.– This is port forwarding.įor home users the most common reason to use port forwarding is gaming. However if you want, for example, to host a website on your internal network and that website needs to be accessible to external clients then you will need to use a standard port ( port 80 for http) as the external client expects this. The ports used by NAT are normally randomly assigned which is OK when the session is initiated from the Internal network. The NAT router maps those packets and re-transmits those packets on the Internal network to the Internal IP address and internal port. The NAT router maps an Internal IP address + Internal Port to the external IP address + external port.Įxternal devices send packets to the external IP address and external port. The IP addresses on the Internal network are private addresses and are not routable on the Internet.Įxternal computers or devices only see the public IP address that is assigned to the NAT router Interface. On home or small office networks the router uses NAT (Network Address Translation) which allows internal devices to share a single external IP4 Address. Client port numbers are dynamically assigned and can be reused once the session is closed. Our PC – IP1+port 2040 -–Yahoo IP3 +port 80 (standard port) Your PC – IP1+port 2020 -– Google IP2 +port 80 (standard port) One looking at the Google website and the other at the Yahoo website. Imagine sitting on your PC at home, and you have two browser windows open. See Network Ports ExplainedĪs an example. The combination of IP address plus port is known as a socket. e.g Web servers normally use port 80 and SMTP servers use port 25. Standard Port numbers are allocated to server services (0-1023) by the Internet Assigned Numbers Authority (IANA). The use of ports allow computers/devices to run multiple services/applications. The port identifies the application/service running on the machine. However a device can run multiple applications/services. On a TCP/IP network every device must have a unique IP address. You will also need to appreciate the difference between internal and external IP addresses and internal and external ports.Ī TCP/UDP port identifies an application or service on a machine in a TCP/IP network. To understand port forwarding you need to understand what a TCP/IP port is and how ports and IP addresses are used together. Most online gaming Applications will require you to configure port forwarding on your home router. It does this by mapping an external port to an internal IP address and port. Port forwarding is a technique that is used to give external devices access to computers services on private networks. What is Port forwarding ? and What Does it do?
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