I ping host1 in my first terminal, it exits with 0 (success).
Then in a separate terminal I ping an unknown host (which fails) and it makes the first ping fails as well!
Here is my best shot at demonstrating the problem:
Note that the first ping will fail for about 15 seconds.
Note also that this doesn't happen for just any hostname. google.com for example works fine. The host that fails is in the local network (10.*).
It's probably a DNS misconfiguration somewhere but I just can't figure out how to debug that thing.