What's with the two interfaces sit0 and sit1 in linux-net-tools

[tigerfishdaisy]

What is with the two IPv6 tunnel interfaces (sit0 & sit1) in linux net tools?  Don't you only need one?

[avenger]

it seems this sit0 is like a generic tunnel enabler, and then you use another (must not be sit1 but also could be something like henet-ipv6 like the autogen script says). Here at home, although I have that sit0, I always set up the sit1, and it is on the sit1 that I set up the endpoint. I don't remember even setting the sit0 up.

That could be for compatibility reasons that we leave sit0 alone.