> It seems if you ifconfig a tunnel (say sit1) and then ifconfig sit1 down
BTW if you will not down it, all the things will be the same.
> and then try to build a tunnel using ip tunnel add the tunnel doesn't
> get built at all;
It is built succesfully, but it is called "sit1" as original creator called it.
Operation "add" identify tunnels by endpoint addresses and do not rename
existing tunnels. New name is ignored.
You should delete sit1 before attempt to create new one
or use "ip link set sit1 name foo".