Sorry, I should have quoted the errors more carefully.
> I wonder why it says DHCP failed instead of no success with DHCP.
You are right, it does say "no success with DHCP".
> If "0.0.0.0" is too short, the chances are "0.0.0.0/0" may be the valid form.
The exact error is "Invalid address length 4 - must be 6 bytes". I tried a few others including 0.0.0.0 but none of them worked. Not specifying this argument however doesn't trigger any complaints.
Perhaps it's time to peruse the man pages for ip! But I have to put this down for now and will come back to it this weekend.