Explanation/Reference:
An extranet is a computer network that allows controlled access from outside of an organization's intranet.
Extranets are used for specific use cases including business-to-business (B2B).

Explanation
Explanation/Reference:
Rebinding would occur.
Rebinding
If the DHCP client is unable to communicate with the DHCP server from which it obtained its lease, and 87.5 percent of its lease time has expired, it will attempt to contact any available DHCP server by broadcasting DHCPRequest messages. Any DHCP server can respond with a DHCPAck message, renewing the lease, or a DHCPNak message, forcing the DHCP client to initialize and restart the lease process.
Note:
Renewing
IP addressing information is leased to a client, and the client is responsible for renewing the lease. By default, DHCP clients try to renew their lease when 50 percent of the lease time has expired. To renew its lease, a DHCP client sends a DHCPRequest message to the DHCP server from which it originally obtained the lease.
Reference: DHCP Client States in the Lease Process

Explanation/Reference:
IPSEC (Internet Protocol Security) is a security protocol that provides encryption and authentication over the Internet. IPSEC supports network-level data integrity, data confidentiality, data origin authentication, and replay protection.