Open Stack

hello all i have an instance with more than 100 days of uptime.it was
mostly idle for months.

For some reason instance was not responding to ping or any network packets.

A Closer look inside vm shows that the dhcp ip received on interface
has expired and a "dhclient" fixed everything (accessed through
console)

Is it normal on an idle system.Is there any way to always keep ip
address available on instances even on idle systems.