I'm dumping DHCP messages with wireshark and running dhclient interface_name to force the dhcp client reconfiguration.
The first time I run dhclient I get all the usual messages: discover, offer, request, ack.
From the second time on, I only get request and ack messages.
Is the machine storing/caching the content from the missing packets somewhere? If so, how do I force the whole message exchange?
dhclient interface_name
actually this command only renews the interface's IP; if it does not have an IP then you will see the full DHCP sequence in order to get one.
if you allways want to force the full DHCP sequence (DISCOVERY, OFFER, etc..) then try the sequence
dhclient -r interface_name
dhclient interface_name