It was brought into Cisco to do that but the project was eventually shelved, which was a shame because the prototypes delivered some really interesting reliability features. Most Cisco hardware products run firmware written in C. Management systems are often Java and (increasingly) Go. Clojure is used for one of the security product lines, but that was developed as a startup that was later purchased by Cisco. One of the management systems, NSO, is written in Erlang (brought in through the tail-f acquisition). There are certainly a lot of people in Cisco that understand the power of Lisp (I was one), but they are spread out and surrounded by people that just want to push whatever the latest thing is (now Go). C.f. the blub paradox and “worse is better.” They have a lot of legacy code that was written over the last 30 years that powers their devices, and that’s all in C.