A+ - IPv4 what is Network ID and Host ID?

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For IPv4 what is Network ID and Host ID?

Hey Andy,

Thank you for the great question! When it comes to these ID's (Network/Host) they help you to identity things:

1- The network that a device is on (Network ID)
2- The unique ID of a host on an individual network (Host ID)

To understand these identifiers it is important to understand where you find them which is IP address. Let's look at the IP address basics to see if this will help you understand. In TCP/IP it is a source and destination IP address that are used to pass traffic to and from devices and for conversation purposes we will call these devices "hosts". In order to identify the two pieces of any IP address (network ID and host ID) we need to apply a subnet mask. The subnet mask is what defines the network portion (network ID) from the host portion (host ID) of any IP address. Now let's change these terms to something we look at more often (at least here in the U.S) which is a street address.

Street addresses also have two components:

A street name:

4th Blvd
4th St
4th Ave

and

A house number

1000 4th Blvd
1000 4th St
1000 4th Ave

Notice how the house number is the same for each of these three street addresses, however they are not on the same street. This is because the street names are different. Well networks work very much the same way. Think of the street name as the network ID and the house number as the host ID. For devices to be able to send traffic to each other within a TCP/IP network all devices must share a common network ID/street name and at the same time EACH device must have a unique host ID or there would be a conflict. Just like on a street, for the mail carrier to deliver to the right mailbox each house must have a unique house number or there would be conflict. Now when a device needs to send data to another network that device will first analyze the network that it is on by the network ID (street name) then inspect the destination IP address of the device. If the source and destination IP addresses have matching network IDs (street names) then they are on the same network and if the destination IP address has a different network ID (street name) then the destination device is on another network and will past the traffic to a device that can send the information to that other network.

Hey Andy,

Here is an episode in which Dan and Ronnie go into TCP/IP addressing properties:

https://itpro.tv/course-library/a1/tcpip-properties-1/

I do believe this will help give you a greater understanding! Again thank you for a great question as it lead to a great discussion!

Best Regards,

Wes Bryan