Building a Darknet - Network
The first step in deploying a Darknet is to locate a suitable home. We recommend first determining the amount of address space you plan to allocate to the Darknet. At a minimum we recommend a /24, though smaller address space - even up to a /32 - will work. You could even allocate a single /32 from each of several /24s to make the Darknet very difficult to detect. The more address space you allocate to the Darknet, the greater your visibility and statistical sampling.
Remember the rule of routing - the most specific prefix wins. This is a great advantage for a Darknet. If you have a /16 for your enterprise, you can route the entire /16 to your Darknet, with more specific routes in your IGP carrying production traffic to the proper places. As with all things, carefully ponder and test this configuration prior to deployment.
Do not use bogon address space. Bogon space is avoided by many scanners and malware. Because bogon space does not include vulnerable hosts, there is no return on the investment for the malware. Use only allocated, routed space for the Darknet.
Note: While this document uses IPv4 exclusively, an IPv6 Darknet is also a viable solution. Future versions of this document may include IPv6 examples, depending largely on Rob's caffeine intake.
A /32, not within the allocated Darknet space, needs to be assigned for both the management IP and the sniffer IP.
The next step is to set aside the physical and logical space for the Darknet. You will need:
The Darknet IP prefix.
A sniffer IP NOT in the Darknet space.
A management IP NOT in the Darknet space.
A distinct VLAN or hub for the Darknet space.
We strongly recommend against putting the Darknet in the same collision domain or VLAN as other subnets. The goal of the Darknet is to provide credible data, thus it is critical to avoid "poisoning" the Darknet with legitimate traffic.
We recommend against putting the Darknet IPs into your publicly visible DNS. DNS RRs such as darknet-sniffer.your.net are just a bit obvious.