IS-IS does not use IPv4 or IPv6, so it should be a no-brainer to run it over IPv4 unnumbered or IPv6 LLA interfaces. The latter is true; the former is smack in the middle of the It Depends™ territory.

Want to know more or test the devices you’re usually working with? The Running IS-IS Over Unnumbered/LLA-only Interfaces lab exercise is just what you need.

Click here to start the lab in your browser using GitHub Codespaces (or set up your own lab infrastructure). After starting the lab environment, change the directory to basic/7-unnumbered and execute netlab up.