Are you trying this on from one of our training courses? More context is needed.
If you're trying this from your machine connected to the internet, it will never work.
Considering example.com is owned by iana and is not a valid domain. and IP 172.25.254.254 is in private range (172.16.0.0 -- 172.31.255.255)
It would appear that you are either working through a lab environment and one of your content hosts are down, or you are having an internal DNS resolution issue in your lab environment.