Answer:
Click FILE > Save, pick or browse to a folder, type a name for your document in the File name box, and click Save. Save your work as you go - hit Ctrl+S often.

Answer:
The network is accesible just for the whitelisted clients configured in the switch connected to the DHCP server
Explanation:
DHCP snooping main task is to prevent an unauthorized DHCP server from entering the our network.
Basically, in the switch we define the ports on which the traffic of the reliable DHCP server can travel. That is, we define as “trust” the ports where we have DHCP servers, DHCP relays and trunks between the switches.