Chapter 20. FlexRoute

Switches started out being strictly Layer 2 (L2) devices until the advent of the Layer 3 (L3) switch, which, if you are as old as me, you might remember were called brouters at their inception. Brouter, being a portmanteau of the words bridge and router, was not the kind of word that people enjoyed saying and so was mostly lost to the realm of forgotten terms. “Hey boss, we need another brouter!” <shudder>

Although switches have been able to “do Layer 3 stuff” for a very long time now, it was mostly a convenience thing that allowed us to build networks without having to resort to another terrifically named network design called router on a stick. What can I tell you—it was the 90s. L3 switches really changed things in the networking world; although they allowed us to route VLANs between one another, they weren’t really routers. This lesson was learned by me the hard way when I decided to have a major provider deliver an OC3 link with an Ethernet handoff so that I didn’t need to spend big money on a router. Routers had WAN interfaces and WAN interfaces were expensive, so I outsmarted the whole system. Hah!

Well, as I soon learned, back then routers supported all sorts of things like QoS and traffic-shaping that we needed, whereas Layer 3 switches did not. Although my L3 switch could route, it wasn’t a real router. Remember, too, that routers often did some heavy lifting at the internet edge where Border Gateway Protocol (BGP) was needed. Supporting full internet ...

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