This short post demonstrates the power of NSX. My example is a DMZ full of webservers – you don’t want any of your webservers talking to each other. If one of your webservers happens to be compromised, you don’t want the attacker to then have an internal launching pad to attack the rest of the webservers. They only need to communicate with your application or database servers.
We’ll use my lab’s Compute Cluster A as an a sample. Just pretend it’s a DMZ cluster with only webservers in it.
I’ve inserted a rule into my Layer 3 ruleset and named it “Isolate all DMZ Servers”. In my traffic source, you can see that you’re not stuck with IP addresses or groups of IP addresses like a traditional firewall – you can use your vCenter groupings like Clusters, Datacenters, Resource Pools, or Security Tags to name a few.
I add Computer Cluster A as the source of my traffic. I do the same for the destination.
My rule is now ready to publish. As soon as I hit publish changes, all traffic from any VM in this cluster will be blocked if it’s destined for any other VM in this cluster.
Note that these were only Layer3 rules – so we’re secured traffic going between subnets. However, nothing’s stopping webservers on the same subnet from talking to each other. No worries here though, we can implement the same rule at layer 2.
Once this rule gets published, even VMs that are layer 2 adjacent in this cluster will be unable to communicate with each other!
This is clearly not a complete firewall policy as our default rule is to allow all. We’d have to do more work to allow traffic through to our application or database servers, and we’d probably want to switch our default rule to deny all. However, because these rules are tied to Virtual Center objects and not IP addresses, security policies apply immediately upon VM creation. There is no lag time between VM creation and application of the firewalling policy – it is instantaneous! Anybody who’s worked in a large enterprise knows it can take weeks or months before a firewall change request is pushed into production.
Of course, you still have flexibility to write IP-to-IP rules, but once you start working with Virtual Center objects and VM tags, you’ll never want to go back.