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Lease renewal

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

Lease renewal is the DHCP procedure by which a client requests continuation of an existing address lease.

Lease renewal keeps a DHCP-assigned address usable after its temporary lease would otherwise expire. The client typically begins at 50% of the lease time, sends a unicast REQUEST to the original DHCP server, and receives an ACK that extends the lease. section 4.1.1

Key operational facts:

  • DHCP leases are temporary; public Wi-Fi may use minutes or hours, while home networks may use 24 hours or more. section 4.1.1
  • Renewal differs from initial DORA assignment: the REQUEST is unicast to the server leasing the address, rather than serving the initial discovery exchange. section 4.1.1
  • The server confirms renewal with an ACK, after which the client continues using the address and other DHCP-provided parameters. section 4.1.1
Figure 4.2 Leasing an IPv4 address via DHCP (the DORA process): (1) DISCOVER from client to server, (2) OFFER from server to client, (3) REQUEST from client to server, (4) ACK from server to client.

Use the DORA message sequence to distinguish initial DHCP leasing from the later unicast renewal REQUEST. section 4.1.1

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes
Explains the renewal trigger, unicast REQUEST, server ACK, and lease-duration examples, but omits configuration and troubleshooting.
Examples
Uses public Wi-Fi leases lasting minutes or hours and home-network leases lasting 24 hours or more.
What it assumes
Assumes familiarity with DHCP leasing and DORA while defining dynamic addresses and renewal behavior.
What you can do after
Apply lease renewal by recognizing its timing and distinguishing its unicast REQUEST and ACK exchange from initial DORA leasing.
How it connects
Connects DHCP lease renewal with DORA, dynamic IP addresses, DHCP servers, and lease duration.
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