In a recent podcast there was some discussion that it sounded like the term Micro Segmentation was being used where it was really traditional segmentation. So I thought I would put out a few thoughts on this front.

What is Segmnentation in Networking

Segmentation is a methodology to create separatet zones of sorts of various traffic types. Various places you may want to do this is within a campus environment to separate students from faculty, or engineering from finance. The list of examples goes on and on. Go to a basic reading of VLANs and you will get the idea of what segmentation is. Once you have VLANs, really segmentation then builds upon this and allows policy to be applied. This policy can be whether or not hosts should be able to talk to each other, or various traffic treatments (QoS). This is something that is well covered already and I do not wish to cover more.

What is Micro Segmentation?

So the newer term is Micro Segmentation. This is exactly as what was covered before but doing it at an even more detailed level. This is getting into being able to apply policy to individual hosts within a segment, creating a micro-segmentation effort.

In Practice


Source Host Destination Host Able to apply policy - Segmentation Able to apply policy - Micro Segmentation
Host A Host B No Yes
Host A Host C No Yes
Host A Host D Yes, at that L3 device/firewall Yes
Host B Host C No Yes
Host B Host D Yes, at that L3 device/firewall Yes
Host C Host D Yes, at that L3 device/firewall Yes

Given the diagram above of two network segments with a firewall in between, we will cover what you can enforce policy with and what you can’t. In this drawing this is a firewall that separates the network segments. However, you could also have this be a L3 device, such as a L3 switch, or a router where there are ACLs in place.

With traditional segmentation, you can apply policy only between the two segments. Host D will have policy applied to try to talk with Host A, B, or C. Host A, B, and C will be able to communicate between each other without any policy being applied.

Micro Segmentation

In that same diagram with Micro Segmentation practices applied, not only can you have policy applied between Host D and the trio of hosts (A, B, C), but you can also apply policy between hosts A, B, C on the same network segment. So if you wanted to lock down so that Host A can only talk out of the segment, but not to any other hosts within the same segment, this is possible. This is the major difference between standard Segmentation and Micro Segmentation, the ability to prevent east-west traffic between hosts in the same network segments.

How to?

So how is this done you may ask? There may be more ways about this, but the ones that I’m aware of are:

Does this work?

Absolutely. I have done host to host policy enforcement within a VLAN using Cisco ISE in a campus LAN environment. There was a requirement to prevent one host to talk to any other host within the same network segment. Cisco ISE definitely delivered on this, within the policy matrix by defining policy that a tag (say 6) could not talk to that same tag (6). If you have some unmanaged switches in the wire that don’t have the hosts wired up directly to a switchport, this is no longer feasible.


So in summary, hopefully this helps clear up some ideas about what Segmentation and Micro Segmentation are in the industry. This is my take on what the difference between Segmentation and Micro Segmentation and that there is a difference. Not just segmenting at a L3 boundry.


I have not figured out yet how to add disqus to the blog at this point. Hopefully I can get that added soon.


Drawing completed at