Category Archives: Network Zoning

Network Zoning – Be the Zone

A while back I started a series on Network Zoning and like most procrastinating, over-achievers: I got side-tracked (is that a self-induced form of ADD?) ! I have had the pleasure of interacting with a number of folks on the zoning topic, and so I wanted to take a moment to tack on an additional concept that doesn’t always get much attention but is very relevant in your network zoning design.

PERSPECTIVE and the impact of perspective.

Perspective in Network Zoning is a little like determine the perspective of an email without knowing the sender. If you’ve ever sent a witty email to someone who didn’t share your sense of humor, you’ve been impacted by perspective. Please be careful not to confuse perspective with context. Perspective deals with a vantage point, while a context is the surrounding details.

When zoning, the perspective of the actual components, users, and threats dictates a given device’s zoning requirements. Theoretically perspective actually defines the security posture.

Did that hurt? Just a little?

Sample Four-Zone Network

The configuration for each of these devices in this illustration is relative to their location in the network. Their perspective determines their configuration. Obvious right? Please keep in mind, the External Firewall or Internal Firewall could easily be a router with ACL’s

Consider that the External Firewall in this illustration sees untrusted incoming traffic and passes only traffic based on rules for the more-trusted networks.

This “trusted” traffic of the External Firewall is actually UNTRUSTED TRAFFIC for the Internal Firewall! After all this is the UNTRUSTED interface on the Internal Firewall.

The Internal firewall can be configured with the same blocking rules of the External Firewall in addition to new rules that are applicable to protecting the Internal Networks.

The addition or the difference in security configuration for internal or external firewalls will be controlled in-part due to perspective because you could obviously implement the same overall security policy on both firewalls but the expectation for what threats exist where will be based on perspective.

In the same light, your zones will have traffic or usage patterns and requirements relative to their placement in the network. External DNS servers will be configured and protected differently than Internal DNS servers. Network resources talking across zones will work differently than talking inside a zone. Your security practices and configuration will change accordingly. The configuration for a given zone will be driven by perspective – requirements will map out differently based on the perspective of users, threats, and policies.

Perspective will show up within the logs as well. When you review the logs on your devices, you will react differently to external threats to your internal servers logged on the actual internal server versus the External Firewall.

When you build out your network zone, be sure to keep perspective in mind. You may choose to overlap policies as a defense in depth practice, but please take care to define your zoning appropriately.

What’s your perspective?
Drop me a line and let me know!