I had Django listening on 127.0.0.1:8000 (default)
As explained in Mitchell’s answer here: Vagrant’s port forwarding not working I should have been listening on 0.0.0.0. Here is a quote of his answer:
I wanted to add an additional note that often this is caused by the
server within the VM because it binds to 127.0.0.1, which is loopback.
You’ll want to make sure that the server is bound to 0.0.0.0 so that
all interfaces can access it.
If you’re using Django, you want to start the dev server like this: ./manage.py runserver 0.0.0.0:8000