Add mininet walkthrough (#7736)

books/free-programming-books-subjects.md

@@ -614,6 +614,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [Kafka gentle introduction](https://www.gentlydownthe.stream) - Mitch Seymour
 * [Kafka, The definitive Guide](https://assets.confluent.io/m/1b509accf21490f0/original/20170707-EB-Confluent_Kafka_Definitive-Guide_Complete.pdf) - Neha Narkhede (PDF)
 * [Linux IP Stacks Commentary](https://www.satchell.net/ipstacks/) - Stephen Satchell, H. B. J. Clifford (HTML) *(:construction: in process)*
+* [Mininet Walkthrough](https://mininet.org/walkthrough/)
 * [Network Science](http://networksciencebook.com) - Albert-Laszló Barabási
 * [Networking! ACK!](https://wizardzines.com/zines/networking/) - Julia Evans (PDF)
 * [Securing Wireless Networks for the Home User Guide](https://mohamedation.github.io/securing-wifi/index-en.html) - Mohamed Adel (HTML)