Adrian Chadd writes [on Cisco's TCAM-based 7600/Cat6500 routers]:
Its a great sale; they suddenly have hard limits which "the internet exceeds", forcing the hardware upgrade cycle. Remember how long the Cisco 75xx persisted and note how many people are still running Cisco 720x's with NPE-225's or NPE-400's w/ full tables simply by adding RAM.
"Simply adding RAM" may not be that easy/cheap, especially when you have to upgrade it on many linecards (VIP2s anyone?). On distributed platforms with hardware forwarding in the linecards (GSR) this is/was probably even worse, you have these "hard limits" in the linecards. Replacing centralized switching engines from time to time doesn't seem such a bad value proposition compared to replacing/memory-upgrading line cards. -- Simon. (Who doesn't care much because we're running at ~30'000 IPv4 routes.)