I'm new to networking and am trying to get my terminology straight. I've Google this question but haven't found anything that clearly explains it.

  • Can you add a bit more information about what exactly you are not sure about? I have never come across the term "netblock". Aug 25, 2016 at 19:06
  • @MarkoPolo Have you tried googling it? I think its shorthand for network block.
    – Nathan
    Aug 25, 2016 at 19:32
  • Yes I Googled it and there are very few references to the term. Definitely not a common term which is why I was curious about context. Aug 25, 2016 at 19:33
  • Is network block more common?
    – Nathan
    Aug 25, 2016 at 19:34
  • In what context? What are you trying to describe? Aug 25, 2016 at 19:35

2 Answers 2


I'm not sure that there is an official definition of "netblock", but in common usage, I've most frequently heard it used in reference to an IP address allocation assigned by an RIR to another organization.

"Subnet", on the other hand, is a more broad networking concept, used when referring to a portion of the IP addresses that are part of a larger network scope.

So, to use these terms together, I will use this fictitious situation:

  • ARIN has allocated the netblock to MyBigCorporation
  • MyBigCorporation needs to subdivide this allocation into smaller subnets for various purposes, so...
  • MyBigCorporation allocates (a subnet of for use by their inbound MXes
  • This is as I understand it in a MSO context.
    – Andrew B
    Aug 25, 2016 at 19:39

A word about the word subnet:

The word subnet is, IMO, incorrectly used most of the time from a purely technical definition. What people generally refer to as a subnet is actually just a network. A subnet is when you take a network and divide it into smaller networks, hence subnetworks, or subnets.

If my internal company network is then that is my network, it is not a subnet. If I break that network into smaller /24 networks then I have created subnets from that network.

If I have a network and a network then I have two networks, not two subnets. A subnet is a logical division of an IP network.

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