Rule 6—Use Homogenous Networks
We are technology agnostic, meaning that we believe almost any technology can be made to scale when architected and deployed correctly. This agnosticism ranges from programming language preference to database vendors to hardware. The one caveat to this is with network gear such as routers and switches. Almost all the vendors claim that they implement standard protocols (for example, Internet Control Message Protocol RFC792,11 Routing Information Protocol RFC1058,12 Border Gateway Protocol RFC427113) that allow for devices from different vendors to communicate, but many also implement proprietary protocols such as Cisco's Enhanced Interior Gateway Routing Protocol (EIGRP). What we've found in our own practice, as well as with many of our customers, is that each vendor's interpretation of how to implement a standard is often different. As an analogy, if you've ever developed the user interface for a Web page and tested it in a couple different browsers such as Internet Explorer, Firefox, and Chrome, you've seen firsthand how different implementations of standards can be. Now, imagine that going on inside your network. Mixing Vendor A's network devices with Vendor B's network devices is asking for trouble.
This is not to say that we prefer one vendor over another—we don't. As long as they are a "reference-able" standard utilized by customers larger than you, in terms of network traffic volume, we don't have a preference. This rule does not apply to networking gear such as hubs, load balancers, and firewalls. The network devices that we care about in terms of homogeneity are the ones that must communicate to route communication. For all the other network devices that may or may not be included in your network such as intrusion detection systems (IDS), firewalls, load balancers, and distributed denial of service (DDOS) protection appliances, we recommend best of breed choices. For these devices choose the vendor that best serves your needs in terms of features, reliability, cost, and service.