Azure Networking : Do not forget the impact of Network Security Groups!


In my last post I mentioned that the NSGs (Network Security Groups) had a serious impact on your deployment. So today I’ll be doing a quick demo a possible annoyance you might encounter.

The demo environment

About the same setup as the last time… One VNET, three subnets ; firewall in subnet, one server in and another server in

2016-03-14 20_08_17-Settings - Microsoft Azure

When taking a firewall from the marketplace, these appliances are typically deployed with NSGs attached. By default you get no outgoing rules & a few incoming rules.

2016-03-14 20_19_46-Outbound security rules - Microsoft Azure

So we’ll be doing a test with the NSGs as deployed by default. And then afterwards change them to the ones underneath…

2016-03-14 20_21_35-Outbound security rules - Microsoft Azure

2016-03-14 20_24_47-Inbound security rules - Microsoft Azure

The Test

2016-03-14 20_26_08-kvaes@ubuntu01_ ~

  • The first ping is between the two servers. No issues there…
  • The second ping is to an external host and that one fails.
  • So we’ll add the rules as specified above… and give it some time (don’t be impatient like me!)
  • And then we see the ping succeeding!


Be aware of the impact of NSGs! You are using two sets of firewalls. So keep your focus or some actor will interfere with your network flow without you realising it immediately!

(sidenote; I do NOT advise using these NSG rules for production workloads!)

One thought on “Azure Networking : Do not forget the impact of Network Security Groups!

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