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What are IP headers?

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All traffic going over the internet has IP headers. An IP header is how a packet knows where to travel over the internet. They display information such as the IP version, the length of the packet, the source, and the destination. Below is an example of browsing via web browser.

Screenshot showing an example of an IP header.

The version displays information about the IP protocol. This would be the traffic type such TCP, UDP, IPv4, IPv6, etc.

Header length is exactly as the name implies, it is the header length in terms of bytes.

The source is the IP the packet was sent from. The destination is the target of your request, such as to ping IP xxx.xxx.xxx.xxx.

Spoofing of this IP header is not possible on our network as it takes information from the sending IP and includes it in the header. This is done through use of checksum. Checksum is added to the IP header upon creation of the packet and is then verified by the destination.

You can download and install TCPdump to check the IP headers as well. Here is an example of an IP header request using TCPdump while pinging a server.

Attached is a screenshot of an IP header using TCPdump. It shows traffic leaving the server going to another server.

You can use TCPdump to verify IP headers and troubleshoot issues with various connections. Such as connecting to a web server or SSH to your server. 

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