I'm not sure where the bug is exactly (seems probable it could be an apple
problem), but for the record...
When my laptop roams from my home wifi to my phone hotspot, it retains the
same IP it had on the home network, which doesn't work with the phone network.
Running dhclient manually results in it supposedly getting the same IP:
iwm0: bound to 10.3.3.63 from 172.20.10.1
The only way to get a working IP is to delete the dhclient.leases file, then
run it again. At last:
iwm0: bound to 172.20.10.6 from 172.20.10.1
I'm not sure what can be done. Does ios echo back our suggestion incorrectly?
Does it return some result that dhclient misinterprets? No idea. We could
detect this condition perhaps? Anyway, there's a workaround for affected
people.