Public vs. Private IP

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Hello all,

Could someone give me a good explanation of the difference between a public and a private IP address, preferably with examples?

Also, the Network+ 008 exam objectives mention the RFC 1918 (1.4). I know what that is as a document outlining Public and Private IPs, but I wasn't sure what the objectives are wanting you to know regarding this.

@shawn-handy said in Public vs. Private IP:

Hello all,

Could someone give me a good explanation of the difference between a public and a private IP address, preferably with examples?

Also, the Network+ 008 exam objectives mention the RFC 1918 (1.4). I know what that is as a document outlining Public and Private IPs, but I wasn't sure what the objectives are wanting you to know regarding this.

Public IP addresses are those that are VALID and useful on the internet.

Private IP addresses are those that are INVALID on the internet and cannot be used to route traffic on the internet. RFC 1918 defines these addresses.

I would pay attention to it identify them and know where you would use them in a scenario, e.g., My company has 500 workstations but one internet connection via a router. On the router pick the appropriate IP addresses for the identified interface...

With regards to RFC 1918 (1.4) I went to rfc-editor.org which I gather is the go to place for RFC documents according to IETF.org

I also looked at datatracker.ietf.org

I cannot find any reference to 1.4 or a section 1.4 unless it means the exam objective is 1.4?

There is a version 5 aka BCP5 which is a Best Current Practice and the document also refers to being created in Feb 1996 but the website says updated in 2013-03-02 and also updated by RFC 6761 although that appears to be about special addresses such as multicast and loop back.

I am a little confused as to which document I should be looking at.

Hey @Bill-Norton, thank you for taking the time to post a question, I am not exactly sure what exam you are studying that goes into this amount of depth. There is a section 4 seen here: https://datatracker.ietf.org/doc/html/rfc1918#section-4

However, I am not sure if this helps. Is there a specific topic that you are studying on? However, I do believe this is exam objective 1.4.

Comptia Network +

Probably overkill but just wanted to ensure I was looking at an up to date document.

The explanation of Ronnie’s about classes and first octects was a great way to remember all the classes easily.

Also congratulations on the courses, entertaining, informative and good value compared to other providers

@Bill-Norton thank you very much for the kind words, and when it comes to "overkill" there is nothing wrong with that at all! Please keep the questions coming and let's get you certified!